Calculate the Length of BC in a Circle that has a Radius of √50 | Step-by-Step Tutorial

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  • Опубликовано: 24 дек 2024

Комментарии • 84

  • @parthosaha4170
    @parthosaha4170 3 года назад +3

    Hello sir,love from Bangladesh 🇧🇩🇧🇩🇧🇩

    • @PreMath
      @PreMath  3 года назад +2

      Thank you so much Partho for your continued love and support. Take care dear and stay blessed😃 You are awesome. Keep smiling😊

    • @Mathematician6124
      @Mathematician6124 3 года назад

      @@PreMath, sir would you like to find the radius if the value of BC is given. This will be another fun.

  • @smalin
    @smalin 3 года назад +30

    In step 5, you just guess values for x and y. Your guess happens to be right, but there are other guesses that would have been wrong. You have shown how to check whether a guess is right, but not how to make the right guess.

    • @peterkrauliz5400
      @peterkrauliz5400 3 года назад

      True what you said. In fact, the right answer is 5.1 haha and Mr Phisterer blundered!

    • @peterkrauliz5400
      @peterkrauliz5400 3 года назад

      Sorry, I didn't follow the explanation to the end, Sir PreMath. Bear with me. However, I was sidetracked by the initial result attempts.

    • @안다순-x5g
      @안다순-x5g 3 года назад +1

      Possible explanation if condition; x and y is natural number

  • @harikatragadda
    @harikatragadda 3 года назад +13

    No need to guess X and Y, the problem itself gives a unique solution.
    Extend AB by a and DB by b to meet the circumference.
    Using the Intersecting Chords Theorem,
    we get 2*b=6*a
    and from R²= ((6-a)/2)²+((b+2)/2)²
    a=4, b=12
    BC= √26

  • @alancs85
    @alancs85 3 года назад +1

    My sollution:
    Extended DB and AB, making 2 chords.
    Called DB's extention as x and AB's extension as y.
    DB*x=AB*y
    2x=6y
    x=3y (1)
    Then, by 4r²=DB²+x²+AB²+y² found that
    x²+y²=160 (2)
    Then, inserting (1) into (2) found that
    x=12 and y=4.
    Then I extended BC, calling one part as √50+BC and the other as √50-BC.
    Then, picking one of the other two chords, found BC
    2*12=(√50+BC)(√50-BC)
    BC=√26

    • @soumyaroy5796
      @soumyaroy5796 2 года назад

      Why 2*12 =( BC+√50)(√50-BC)?? Is there any relation fir using this?

    • @alancs85
      @alancs85 2 года назад

      @@soumyaroy5796 It's Intersecting Chords Theorem. When you extended BC, one part os the chord is √50+BC and the other is √50-BC, becouse the given radius is √50.

    • @soumyaroy5796
      @soumyaroy5796 2 года назад

      @@alancs85 got the clear picture. Thanks!

  • @qqqquito
    @qqqquito 3 года назад +4

    8:18 Can x and y be picked freely as long as making x+3y=8? No. It has to be obtained by solving either Eq. 1 or 2.

  • @williamjones2407
    @williamjones2407 3 года назад +3

    I have been out of school for a long time.
    This man would have been a great teacher for math class 👏

    • @PreMath
      @PreMath  3 года назад +1

      Thanks William for such an elegant feedback. Thank you so much for taking the time to leave this comment. You are awesome 👍 Take care dear and stay blessed my friend😃

  • @marioalb9726
    @marioalb9726 Год назад +1

    tan β = 6/2
    β = 71,565°
    Labelling point 'F' to the extension of '2' intersecting the circumference
    DF = DB + BF = 2 + a
    ACF is isosceles triangle
    R sin β = ½ FA
    FA = 2 R sin β
    FA = 2 √50 √0,9
    FA = √180 = 13,416 cm
    FA² = 6² + a²
    a = 12 cm
    Intersecting chords theorem:
    (R+z)(R-z) = 2 . a
    R²-z² = 2 . 12
    z² = R² - 2 . 12
    z² = 50 - 24 = 26
    z = √26 cm ( Solved √ )

  • @murdock5537
    @murdock5537 2 года назад +1

    Great challenge, awesome way to solve it - especially "let's pick some x and y values..."
    (2 + a)^2 + (6 - b)^2 = a^2 + b^2 →
    a = 3b - 10 → (b - 3)^2 = 4 → b1 = 5; b2 = 1 → a = 3b - 10 > 0 → b = b1 = 5 →
    a = 15 - 10 = 5 → BC = √26
    obviously:
    a > 2
    b < 6
    and:
    a^2 + b^2 = 50 → 50 = 2(25) = 2(5)^2 → a = b = 5
    or:
    tan⁡(θ) = AB/BD = 3 → θ = 71,565°
    AF = DF = AD/2 = √10 → tan⁡(φ) = √10/√40 = √(1/4) = 1/2 → φ = 26,565°→
    γ = DAC = 90° - φ = 63,435°→
    θ + γ = 135° → AR = a = CR = b = √50/√2 = √25 = 5 = a = b → 25 + 1 = (BC)^2
    (AR = parallel to DF; CR = parallel to AB)
    Another approach:
    tan⁡(α) = BD/AB = 2/6 = 1/3 → α = 26,57°
    (AD)² = 4 + 36 = 40 → AD = 2√10.
    AD/2 = AF = DF = √10 → (CF)^2 = (AC)^2 - (AF)^2 = 50 - 10 = 40 →
    CF = 2√10 = 2AF = 2DF = AD
    Draw x- and y-axis:
    x = horizontal through A;
    y = AB → find the coordinates of Point F →
    F cuts AD in half → A(0; 0) → D (-2; 6) → F(-1; 3)
    two equations to solve the problem:
    f(x) = g(x) in F(-1; 3)
    f(x) = AD = -3x
    g(x) = (x/3) + k → g(x) = 3 = (-1)/3 + k → k = 10/3 → g(x) = (x/3) + (10/3)
    f(x) = g(x) → crossing in Point F
    FC' = parallel to DB → CC' = parallel to AB → (CC')/(FC' ) = 1/3 = tan⁡ α →
    (FC)^2 = (FC' )^2 +(CC') = 40 = a^2 + (3a)^2 = 10a^2 → a^2 = 4 → a = 2 →
    CC' = 2 → FC' = 6 → (BC)^2 = √(25 + 1) = √(26) 🙂
    or:
    tan⁡(δ) = BD/AB = -3 → tan⁡(α) = (CC')/(FC' ) = 1/3 →
    CF = √40 = 2√10 → CC' = k → (CF)^2 = 40 = 10(k)^2 →
    k = √4 → k = 2 (s.t.: k > 0) →
    CC' = k = 2 → FC' = 6 → B'C' = a = 6 - 1 = 5 = b → BC = √26

    • @PreMath
      @PreMath  2 года назад

      Excellent!
      Thanks for sharing! Cheers!
      You are awesome. Keep it up 👍
      Love and prayers from the USA! 😀
      Stay blessed 😀

  • @DutchMathematician
    @DutchMathematician 3 года назад +1

    As many have stated here... guessing and then checking afterwards is NOT the right way to go. It could be that a problem has more than one solution for the length x, e.g.
    The easiest way to proceed from @8:00 (still only using Pythagoras' theorem to solve this problem) is as follows:
    Consider ΔACE:
    - AE = 6 - y
    - EC = x = 8 - 3y
    - AC = √50
    Applying Pythagoras' theorem in this triangle (AC^2 = EC^2 + AE^2) gives:
    50 = (8 - 3y)^2 + (6 - y)^2
    Expanding the squares and simplifying the resulting expression yields:
    y^2 - 6*y + 5 = 0
    This quadratic equation has two solutions: y=1 and y=5.
    Since x = 8 - 3y, this leads to x = 5 or x = -7.
    Since x represents a length (and must therefore be positive), we can ignore the solution y = 5.
    Therefore (x, y) = (5, 1) is the only solution.
    Now proceed with this result at @10:06.

  • @marioalb9726
    @marioalb9726 Год назад +1

    tan α = 2/6
    α = 18,435°
    Labelling point 'E' to the extension of '6' intersecting the circumference
    AE = AB + BE = 6 + b
    R sin α = ½ ED
    ED = 2 R sin α
    ED = 2 √50 √0,1
    ED = √20 = 4,472 cm
    ED² = 2² + b²
    b = 4 cm
    Intersecting chords theorem:
    (R+z)(R-z)=6.b
    R²-z² = 6.b
    z² = R² -6.b
    z² = 50 - 6 . 4 = 26
    z = √26 cm ( Solved √ )

  • @shadrana1
    @shadrana1 3 года назад

    Use the sketch at 3:46,
    r=sqrt(50),
    Take the Intersecting Chord Theorem,
    About F,
    (x+2)^2=(r-y)(r+y)
    x^2+4x+4= r^2-y^2=50-y^2
    x^2+y^2=46-4x.............................(1)
    About E,
    (6-y)^2=(r-x)(r+x)
    y^2-12y+36=r^2-x^2
    y^2+x^2=14+12y..........................(2)
    Equate equations (1) and (2),
    46-4x=14+12y
    12y+4x=32,3y+x=8
    y= (8-x)/3.....................................(3)
    Use the triangle DFC,
    DF^2+FC^2=r^2
    (x+2)^2+y^2=(sqrt(50))^2
    (x+2)^2+((8-x)/3}^2=50 (substitute y from (3)),
    x^2+4x+4+(x^2-16x+64)/9=50
    9x^2+36x+36+x^2-16x+64=450
    10x^2+20x+100=450
    x^2+2x+10=45
    x^2+2x-35=0
    (x-5)(x+7)=0
    x=5, reject the -ve root.
    y=(8-x)/3 from (3),
    =(8-5)/3,y=1.
    From sketch, BC^2=x^2+y^2=46-4*5=26, from (1)
    BC=sqrt(26) units and that is our answer.
    This is a good place to stop.
    Thanks for the problem PreMath.

  • @rssl5500
    @rssl5500 3 года назад +1

    Hello but I’m the last why did you pick whole numbers? It could have also been irrational or numbers that are not integers and that was not mentioned in the question

  • @timeonly1401
    @timeonly1401 2 года назад

    Wow.. this was tougher than it looked at first blush! Thx.

  • @ebi2ch
    @ebi2ch 3 года назад +3

    Here is another solution.
    Extend AB and let E be the point where it intersects the circle. From the angle of circumference theorem, angle DCE is twice angle DAE. Also, CD and CE are equal in length, so triangle CDE is an isosceles triangle. If we draw a line bisecting angle DCE and set F as the intersection with DE, then angle DFC is a right angle. Therefore, triangle ABD and triangle CFD are similar. From the similarity ratio, the length of DF is the sqrt 5. The length of DE is twice that of DF. Finally, extend BC in both directions, and let G and H be the intersections with the circle, respectively. the length of BG is the radius-x. the length of BH is the radius+x. Therefore 4*6=(x-radius)(x+radius). 24=x^2-50. x^2=26. x=sqrt 26.

    • @ebi2ch
      @ebi2ch 3 года назад +1

      The explanation was missing, so I'll add it.
      Using the Three Square Theorem, DE^2-DB^2=BE^2. Therefore BE^2=20-4=16. Therefore BE=4.

    • @안다순-x5g
      @안다순-x5g 3 года назад +1

      説明内容に従って絵を描きました.理解しました。すごい

    • @ebi2ch
      @ebi2ch 3 года назад

      @@안다순-x5g ありがとう!

    • @hrisheekeshbhave5607
      @hrisheekeshbhave5607 3 года назад +1

      @@ebi2ch And also extend BC not BE

    • @ebi2ch
      @ebi2ch 3 года назад

      @@hrisheekeshbhave5607 Your explanation is correct. This was a simple typo on my part. Thank you for pointing it out.

  • @blobfish1112
    @blobfish1112 3 года назад +2

    First calculate AD, then

  • @hrisheekeshbhave5607
    @hrisheekeshbhave5607 3 года назад +1

    Guessing and checking is no solution. To solve, say x,y is remaining lengths of two given intersecting cords having 6,2 as part lengths respectively. This amount to y=3x as products of segments of intersecting cords are equal. Now draw diameter parallel to any cord and find x using Pythagorean triplet relation. This would give x=4 and thus y=12. Then find BC=√26, again using Pythagorean triplet relation. This is the correct way.

  • @destruidor3003
    @destruidor3003 3 года назад

    I understood how to find the correct solution.
    The two equations obtained by pitagoras are equations of circunference so you need to draw both grafics.
    Then you find the interception between both circunferences points (5,1) and (-7,5). The equation x+3y=8 is going to intercept both points. The point (-7,5) has only physical meaning if we use a system of coordenate relative instead of distances.

  • @Kkkkkkk-d8k
    @Kkkkkkk-d8k 3 года назад +1

    Sir I want to send you some problems where do I send?

  • @JLvatron
    @JLvatron 2 года назад

    I used Trig.
    1- Pythag AD, then Trig to calculate angle DAB.
    2- Connect CA & CD to get triangle CAD, with all known side values. Law of Cos to calculate angle CAD.
    3- Now look at triangle CAB. Angle CAB = (angle CAD - angle DAB)
    4- Now triangle CAB has 2 known sides and middle angle.
    Law of Cos to calculate distance CB, our answer.

  • @procash1968
    @procash1968 3 года назад

    Beautifully explained Sir

  • @AbhishekSingh-qn4bz
    @AbhishekSingh-qn4bz 3 года назад +2

    Awesome video solution sir...I understood everything.. thank you very much 👍👍

    • @PreMath
      @PreMath  3 года назад +1

      Great 👍
      Thanks Abhishek for such an elegant feedback. Thank you so much for taking the time to leave this comment. You are awesome 👍 Take care dear and stay blessed😃

  • @mariamenezes5850
    @mariamenezes5850 3 года назад +2

    Sir can you please solve this ....
    Decompose to partial fractions :
    1) 2(x^2-3x+2) / x^3+2x-3
    2) 54 / x^3-21x+20

    • @晓阳-d3p
      @晓阳-d3p 3 года назад

      photo math ,the app on phone ,inside have calculater

  • @starain_
    @starain_ 2 года назад

    In step 5, x+3y=8 , let y=t , x=8-3t ( t>0 , 8-3t>0) = ( 0

  • @hijodebakunin
    @hijodebakunin 3 года назад

    Theorem of Chords:
    x • z = w • y
    2 • z = 6 • y
    z = 3y (1)
    Perpendicular Chords:
    4r² = x² + y² + w² + z²
    4(√50)² = 2² + y² + 6² + z²
    200 = 4 + y² + 36 + z²
    200 = 40 + y² + z²
    160 = y² + z² (2)
    (1) & (2) ==> 160 = y² + (3y)²
    160 = y² + 9y²
    160 = 10y²
    16 = y²
    ==> y = 4 (3)
    Theorem of Chords:
    6 • y = (√50 + BC) • (√50 - BC)
    6y = (√50)² - (BC)²
    (BC)² = 50 - 6y (4)
    (3) & (4) ==> (BC)² = 50 - 6 • 4
    (BC)² = 50 - 24
    (BC)² = 26
    BC = √26

  • @johnbrennan3372
    @johnbrennan3372 3 года назад +5

    Used different construction and used cosine rule three times giving me square root of 26

    • @PreMath
      @PreMath  3 года назад +1

      Incredible John! Smart move.
      Thanks dear for sharing. You are awesome 👍 Take care dear and stay blessed😃

  • @johnbrennan3372
    @johnbrennan3372 3 года назад

    Can also be done using cosine rule three times

  • @123rockstar2010
    @123rockstar2010 2 года назад +1

    3:34 This problem is meant to be solved in trigonomeetry to avoid trial and error.
    ∠DAB = artan(2/6) = 18.43°
    ∠DAC = 63.43° (sine rule from isoseles △DCA with both radius =√50 and hypotenuse of △DBA = √40)
    Notice that ∠BAC = 45°!!!~
    ∠ECA = 45°
    Therefore,
    EA = EC = 5 (Pythagorean Theorem of △EAC given AC = √50)
    BE = BA - EA
    BE = 6 - 5 = 1
    So,
    BC = √26 = 5.099

  • @craigjones2075
    @craigjones2075 3 года назад +2

    In the equation x + 3y = 8, another possible solution is (2,2) which was not checked.

    • @jarikosonen4079
      @jarikosonen4079 3 года назад

      Sometimes is it allowed to "guess" and check later?
      In my check (2,2) didn't seem to work with equations (1) & (2).
      Also x=-7, y=5 would work in eq (3), but might be with wrong geometry, of a kind...
      To avoid "guessing", one could try solve coordinate points for A as (-5,-5) and D as (-7,1) and then point B at (-7+2,-5+6)=(-5, 1) and C was at (0,0).
      Then distance from B to C is sqrt((0-(-5))^2+(0-1)^2)=sqrt(26).

    • @LexxKD
      @LexxKD 2 года назад +1

      x=8-3y => x2+(y-6)2=50 => y2-6y+5=0 => y = 1 (true) and y = -5 (wrong).
      I think it's better than guess.

  • @Billlakeview
    @Billlakeview 3 года назад

    Extend DBto the far side of the circle , calling it H, and extend AB. to the top of the circle, calling it G.lNote that if you use the values 1 and 5 that you have in your solution that DBxBH does not equal ABxBG. If you use this chord-chord product theorem, together with the Pythagoras applications in your solution,
    you can find that BC=2sqrt2.

  • @destruidor3003
    @destruidor3003 3 года назад

    I agree that there is a issue with this solution when you say...to make things simple let take interget numbers for x e y ...there is no constraint in the exervise that allows you to say that x and y are intergers so this solution is not really proved..

  • @adityakumarvishwakarma7282
    @adityakumarvishwakarma7282 3 года назад +1

    Sir please make a video on this question next
    Integral from 0 to 2pi(1/(3+2sin(x))dx
    Using contour integrals

    • @PreMath
      @PreMath  3 года назад +1

      Sure Aditya!
      Pretty soon I'll do that. Thanks for asking.
      Take care dear and stay blessed😃

    • @adityakumarvishwakarma7282
      @adityakumarvishwakarma7282 3 года назад

      Thanks sir
      You are best

  • @tomcruise6738
    @tomcruise6738 3 года назад

    Amazing! ♥️🔥
    Greetings and Prayers from India! ❤️🇮🇳

  • @sthinvc
    @sthinvc 3 года назад +1

    actually we can put x=8-3y into equation (1) to solve x and y, no need to guess

  • @javanuwamungu5824
    @javanuwamungu5824 3 года назад +4

    Could also use the chords theorem and solve a quadratic equation in x (or y!) No need to guess then verify! But I have to admit that I struggled a bit before solving this one! EUREKA! 😂😂

    • @PreMath
      @PreMath  3 года назад +3

      Dear Javan, thanks for sharing. Elegant feedback. Thank you so much for taking the time to leave this comment. You are awesome 👍 Take care dear and stay blessed😃

    • @mohammedaamir5081
      @mohammedaamir5081 3 года назад

      How?

  • @destruidor3003
    @destruidor3003 3 года назад

    I found other way to solve . You need to combine the equation of x+3y =8 with one of the circunference equations then you will obtain one equation of second degree where the roots are 5 and 1 then you use these roots in the equation of x+3y=8 to find the value of the other variable.

  • @destruidor3003
    @destruidor3003 3 года назад

    Attention the values 5 and 1 are for y in tne equation of x+3y=8

  • @tahasami3409
    @tahasami3409 3 года назад

    Thank you for premath

  • @ВладимирСтрельников-ф8м

    Довольно интересное решение! Respect!

    • @PreMath
      @PreMath  3 года назад +1

      Большое спасибо, Владимир, за вашу неизменную любовь и поддержку. Береги себя, дорогая, и оставайся счастливым😃 Ты потрясающий. Продолжай улыбаться😊

  • @wolfgangwieser5911
    @wolfgangwieser5911 3 года назад

    Hi, great - this was a hard nut to crack !
    If found the solution with some trigonomertry.
    First I got the angle BCA with the law of cosines, the same with angle DAC - after I got the distance DA .
    Now I calculated angle DAB and found angle BAC . Now the law of cosines again gives the distance BC….

  • @manuelantoniobahamondesa.3252
    @manuelantoniobahamondesa.3252 3 года назад

    excelente profe !

  • @India-jq7pi
    @India-jq7pi 3 года назад +1

    Thank you sir

    • @PreMath
      @PreMath  3 года назад +2

      Thanks Gowri for such an elegant feedback. Thank you so much for taking the time to leave this comment. You are awesome 👍 Take care dear and stay blessed😃

  • @Mathematician6124
    @Mathematician6124 3 года назад

    My solution. First, join C, D and C, A join A, D furthermore. Drop perpendicular from C on AD. Let the foot of the perpendicular be F. CA =CD=root 50 and AD=root over(36+4)=2 (root 10),now Cos(angle CAD) =1/root5 and sin(angle CAD) =2/root5. See, sin(angle BAD ) =1/root10 and Cos(angle BAD ) =3/root10. Now sin(angle BAC)=sin(angle CAD - angle BAD)=(2/root5)(3/root10) - (1/root5) (1/root10) =1/root2=sin45. Drop perpendicular at E on AB, from C. Traingle CEA will be isosceles with EA=EC=root over(50/2)=5 (because angle BAE=45), now BE=6-5=1 and CE=5 therefore BC=root ovet(25+1)=(root 26). This is our ans. I could do it with cosine rule but I preferred doing it step by step by precise construction

  • @EPaozi
    @EPaozi 2 года назад

    Sans se fatiguer 50^.5 -2 est égal environ à 5,071 !!!!! Without getting tired 50^.5 -2 is approximately equal to 5.071!!!!!

  • @saraseba898
    @saraseba898 3 года назад

    But x = square(50) - 2 no?

  • @Mathematician6124
    @Mathematician6124 3 года назад

    Many values of x and y satisfies the equation. Take x=2, y =2 this also does satisfy. But this does not satisfy equation 1 and equation 2. So, it is defined. But too long.

  • @thomasaskew1985
    @thomasaskew1985 3 года назад +1

    That was a bit more challenging.

  • @theophonchana5025
    @theophonchana5025 3 года назад

    Right triangle

  • @Mathematician6124
    @Mathematician6124 3 года назад

    I used trigonometry to solve this. It was an easy one.
    See

  • @theophonchana5025
    @theophonchana5025 3 года назад

    #Pythagoras #PythagoreanTheorem

  • @balakrishnakarri6264
    @balakrishnakarri6264 3 года назад

    I have a genuine solution. Dont use trial and error method. If x and y are not integers then what you do?
    I have simple and clear solution but i cant explain in comment box.

  • @theophonchana5025
    @theophonchana5025 3 года назад

    Square root of 50

  • @theophonchana5025
    @theophonchana5025 3 года назад

    Square root of 26

  • @theophonchana5025
    @theophonchana5025 3 года назад

    Pythagorean Theorem

  • @Teamstudy4595
    @Teamstudy4595 3 года назад

    300 th like

  • @theophonchana5025
    @theophonchana5025 3 года назад

    Pythagoras