Olympiad Mathematics | Find area of the pink square | (Isosceles triangles) |

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  • Опубликовано: 7 авг 2024
  • Learn how to find the area of the pink square. Pink square is inscribed in an isosceles triangle. Important Geometry and Algebra skills are also explained: area of a square formula; Pythagorean Triples; similar triangles; Pythagorean theorem; Isosceles triangles. Step-by-step tutorial by PreMath.com
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    Olympiad Mathematics | Find area of the pink square | (Isosceles triangles) | #math #maths
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Комментарии • 44

  • @dpie4859
    @dpie4859 7 месяцев назад +3

    Very nice and clear explanation. Well done.

    • @PreMath
      @PreMath  7 месяцев назад

      Thanks❤️🌹

  • @JLvatron
    @JLvatron 7 месяцев назад +1

    Brilliant!

  • @user-ii5vr3um9r
    @user-ii5vr3um9r 7 месяцев назад +1

    Draw perpendicular to AC from B, intersecting AC at P. BP=9.6, DG=x, CG=10-x, DG:BP=CG:CB, x:9.6=(10-x):10, x=240/49

  • @zdrastvutye
    @zdrastvutye 3 месяца назад

    i have an idea: vary xf until the perpendicular distance to the left hand line is equal to the intersection on the right hand line while yf=0 all the time
    10 print "premath-olympiad mathematics-find area of the pink square":dim x(4,2),y(4,2)
    20 la=10:lb=10:lc=12:sw=la/(la+lb+lc):lh=(la^2-lb^2+lc^2)/2/lc:h=sqr(la^2-lh^2)
    30 xp=sw:yp=0:yf=yp:x1=0:y1=0:x2=lh:y2=h:xg21=lc:yg21=0:xg22=lh:yg22=h:yg11=0
    40 dx=x2-x1:dy=y2-y1:xa=0:ya=0:xc=lh:yc=h:goto 180
    50 zx=dx*(xp-x1):zy=dy*(yp-y1):k=(zx+zy)/(dx^2+dy^2)
    60 dxk=dx*k:dyk=dy*k:xe=x1+dxk:ye=y1+dyk:xf=xp:dxu=xe-xf:dyu=ye-yf:n=sqr(dxu^2+dyu^2)
    70 xg11=xf:xg12=xg11+dyu:yg12=yg11-dxu
    80 a11=yg12-yg11:a12=xg11-xg12:a131=xg11*(yg12-yg11):a132=yg11*(xg11-xg12)
    90 a21=yg22-yg21:a22=xg21-xg22:a231=xg21*(yg22-yg21):a232=yg21*(xg21-xg22)
    100 a13=a131+a132:a23=a231+a232:gosub 110:goto 160
    110 ngl1=a12*a21:ngl2=a22*a11
    120 ngl=ngl1-ngl2:if ngl=0 then print "keine loesung":end
    130 zx1=a23*a12:zx2=a13*a22:zx=zx1-zx2
    140 zy1=a13*a21:zy2=a23*a11:zy=zy1-zy2
    150 xl=zx/ngl:yl=zy/ngl: return
    160 ls=sqr((xf-xe)^2+(yf-ye)^2):lr=sqr((xf-xl)^2+(yf-yl)^2)
    170 dg=(ls-lr)/lh:return
    180 gosub 50
    190 xp1=xp:dg1=dg:xp=xp+sw:xp2=xp:gosub 50:if dg1*dg>0 then 190
    200 xp=(xp1+xp2)/2:gosub 50:if dg1*dg>0 then xp1=xp else xp2=xp
    210 if abs(dg)>1E-10 then 200 else print "die flaeche des quadrats=";ls^2
    220 lae=sqr((xp-xa)^2-ls^2):dx=lh:dy=h:n=sqr(dx^2+dy^2):dxd=(xc-xa)*(lae+ls)/la
    230 xd=xa+dxd:dyd=(yc-ya)*(lae+ls)/la:yd=ya+dyd
    240 masy=900/h:masx=1200/lc:if masx
    run in bbc basic sdl and hit ctrl tab to copy from the results window

  • @DB-lg5sq
    @DB-lg5sq 7 месяцев назад +1

    شكرا لكم
    CosACB=7/25
    sinACB=24/25
    sinACB=x/10-x
    .....
    x=240/49

  • @johnryder1713
    @johnryder1713 7 месяцев назад

    Merry Christmas Premath and all the subscribers

  • @user-mx8sj1nc6v
    @user-mx8sj1nc6v 7 месяцев назад

    If you put C(0,0) and A(10,0) and B is in the x>0 , y>0 area, CF is the locus of all points where a square is in the triangle, one side is on AC and another vertex is on CB... so you can see that if CB is y=mx then CF is the y= [m/(m+1)]x and you can find F . [ locus of all points of the forth vertex]

  • @hcgreier6037
    @hcgreier6037 6 месяцев назад

    Very smart solution! 🤣
    I took a quick look on the arbitrary solution for the isoceles triangle.
    Let the base of triangle be *c* and the congruent legs be *a*.
    Then, height h will be h = √(a²-c²/4). After a little math mumbo-jumbo one will get:
    x(a,c) = [a·c·√(4a²-c²)] / [2a² + c·√(4a²-c²)], a rather complicated term.
    In this case, we have c = 12, a = 10, therefore x = 10·12·√(4·10²-12²) / [2·10² + 12·√(4·10²-12²)], which gives x = 240/49 ≈ 4.89796. x² = 23.99...
    *Challenge:* Where are the vertices E, D of the square lying on the lefty a-side?

  • @soli9mana-soli4953
    @soli9mana-soli4953 7 месяцев назад

    ABC and FGB are similar having angle in B in common and CAB = GFB because AB and FG are parallel.
    Split triangle GFB in two right triangle with height GH. Their sides are
    GH=8a, BH=6a and GB=10a
    GHB and AEF are similar being right and because angles in B and A are congruent being ABC isosceles, so
    GH : EF = GB : AF
    8a : 10a = 10a : AF
    AF = 25/2a
    AB = AF + FH + BH = 12
    AB = 25/2a + 6a + 6a = 12
    a = 24/49
    side of square = 10a => s = 10*24/49 = 240/49

  • @chrisviviers5649
    @chrisviviers5649 Месяц назад

    How can you assume point P and point F align? There is no guarantee they are the same point.

  • @ScarlettEmeraldASMR
    @ScarlettEmeraldASMR 7 месяцев назад +1

    Just subscribed 😊😊😊

    • @PreMath
      @PreMath  7 месяцев назад

      Many thanks ❤️

  • @batavuskoga
    @batavuskoga 7 месяцев назад +1

    I thought because the triangles ABC and BFG are similar triangles, you could use the angle-angle theorem
    angle at point B = alpha
    angle at point C = angle at point G = beta, because both are isosceles triangles
    AC/AB = FG/BF
    10/12 = FG/6 --> FG = 5
    area square = FG² = 25
    Also 12a = 6, so a = 0.5. side square = 10a = 10*0.5 = 5
    What have I done wrong here ?

    • @fadetoblah2883
      @fadetoblah2883 7 месяцев назад

      It seems you have assumed that F is the middle point of segment AB, which it's not.

  • @roger10coutinho
    @roger10coutinho 6 месяцев назад

    You are looking great, mate. The difference is huge. In the beginning you were like "my stomach hurts, my life is terrible. I don't have any energy." Now, you are full of energy. You want to challenge yourself (exercise daily). You enjoy life. Go to Halloween parties. Don't complaint about anything. You just are bringing the masculine energy from inside and you are being a man. Keep going. Congrats.

  • @misterenter-iz7rz
    @misterenter-iz7rz 7 месяцев назад

    area=8×6=48, h=96/10=48/5, 100-(48/5)^2=2.8^2, other side=10-2.8=7.2, (48/5)/10=48/50=24/25=(48/5-s)/s, 24s=5×48-25s, 49s=5×48, s=240/49, s^2=(240/49)^2=24 approximatel. 😊

  • @user-zg5yd3wl5w
    @user-zg5yd3wl5w 7 месяцев назад +2

    Professor's comon dialogue : Welcome to pre math. 😊. But i scare math. Could you tell me how to love sum. 😢

    • @bigm383
      @bigm383 7 месяцев назад +1

      Just knowing that you are welcome is a start!

    • @PreMath
      @PreMath  7 месяцев назад +3

      No worries. We are all lifelong learners. That's what makes our life exciting and meaningful!
      Just keep watching...
      Take care dear ❤️

  • @giuseppemalaguti435
    @giuseppemalaguti435 7 месяцев назад +1

    Essendo un triangolo isoscele conosco gli angoli e,con il teorema dei seni calcolo a=300/49,b=288/49,a+b=12..per cui l=300/49sin(arccos6/10)=300/49*4/5=240/49

    • @PreMath
      @PreMath  7 месяцев назад

      Thanks❤️

    • @giuseppemalaguti435
      @giuseppemalaguti435 7 месяцев назад

      ​@@PreMathBuon Natale

    • @PreMath
      @PreMath  7 месяцев назад

      @@giuseppemalaguti435
      Merry Christmas❤

  • @andreaitalia7657
    @andreaitalia7657 7 месяцев назад

    I used another method and the area is exactly 24 cm squared, it's not circa 24 but it's exactly 24

    • @dirklutz2818
      @dirklutz2818 5 месяцев назад

      Not so. The value is 23.99000416493127863390254060808...

    • @robertlynch7520
      @robertlynch7520 5 месяцев назад

      @@dirklutz2818 23.990004164931 is what I got too. But my calculator isn't all that precise. LOL

  • @LuisdeBritoCamacho
    @LuisdeBritoCamacho 7 месяцев назад

    At a first glimpse I would say that the Area of the Pink Square is ~ 5^2 su or ~ 25 su
    But if the Point F is the Middle Point between A and B, my answer is 4,8^2 su ~ 23,04 su.
    I'll be back later to prove it.

  • @devondevon4366
    @devondevon4366 7 месяцев назад

    23.999 or 24
    n=4.89796, the length of the square
    let the side of the square = n
    the area of triangle CDG + AEF = (10-n)(n)/2 Since both have the same
    base 'n' and 10-n is the difference of the side n of the square
    the area of CDG + AEF = (10 n- n^2)/2
    one more triangle to go: BFG
    Since BFG is similar to ABC, and CF is 8 (3-4-5 triangle), then
    the two legs of BFG in terms of 'n' are 8/10 (n) and 12/10 (n)
    Hence, the BFG area in terms of 'n' = [ (0.8n)(1.2n)]/2 = 0.96n^2/2
    Area of ABC = 12 * 9 /2 = 48, then this equal
    the area of CDB + AEF, + area of the square + are of BFG = 0.96n/2
    Hence 48 = (10n-n^2)/2 + n^2 + 0.96n^2/2
    96 = 10 n- n^2 + 2n^2 + 0.96n^2 (multiply both sides by 2)
    0 = 1.96n^2 + 10n - 96
    n= 4.89796 (Quadratic formula calculator
    so the length of the side of the square = n
    I had first put the side of the square, but you want the area
    area =4.89796 x 4.89796 = 23.9999

    • @PreMath
      @PreMath  7 месяцев назад

      Great!
      Many thanks ❤️

    • @devondevon4366
      @devondevon4366 7 месяцев назад

      @@skwest Thanks for this comment, but I meant that
      the C and "X' (the midpoint of AB ) is 8 before I looked at the Premath labeling of the diagram: ABCDEFG after working the problem on a sheet of paper. So, when I did look, I somehow used "F" for "X." Thanks again, as you are correct as
      though DE lies on AF , DG does not lie on CB.

  • @user-xq3rn8nq3c
    @user-xq3rn8nq3c 7 месяцев назад +2

    𝙼𝚎𝚛𝚛𝚢 𝙲𝚑𝚛𝚒𝚜𝚝𝚖𝚊𝚜

    • @PreMath
      @PreMath  7 месяцев назад +1

      Thank you very much!
      𝙼𝚎𝚛𝚛𝚢 𝙲𝚑𝚛𝚒𝚜𝚝𝚖𝚊𝚜❤️

  • @robertlynch7520
    @robertlynch7520 5 месяцев назад

    I, apparently, am the most pig-headed algebra guy, ever. I found this problem to be intensely annoying. Approached it 3× from the beginning, because I just couldn't do the algebra without being confused.
    In the end though, several intersecting equations-of-lines solved this.
    First, it is critical to recognize that the height of the ABC triangle is 8 units. Because … ½ of 12 base units with a hypotenuse of [10] units leaves [8] units as the rise. Pythagoras.
    This in turn defines
      f(𝒙) = ⁸⁄₆𝒙 ⊕ 0
      f(𝒙) = ⁴⁄₃𝒙 ⊕ 0
    [⊕0] because it has a (0, 0) origin. Right?
    Then the diagonal “side of the square” (lower one, left) has an inverted line equation:
      f'(𝒙) = -¾𝒙 + B
    So what is the B? Ah … well introduce a new term [𝒂], the bit along the base, from the left which intersects with the corner of where the square meets the rising left triangle side. Because of the line function (the f(𝒙) one), we know that the height is 4𝒂/3 so
      -3𝒂/4 + B = 4𝒂/3 … shift around
      B = 4𝒂/3 ⊕ 3𝒂/4 … find a common denominator and combine
      B = 25𝒂/12
    So, that can be put into the inverted line equation
      f'(𝒙) = -¾𝒙 + 25𝒂/12
    We can use this immediately to find the point on the base, where it intersects.
      0 = -¾𝒙 + 25𝒂/12 … rearrange to solve for 𝒙
      𝒙 = 25𝒂/9
    ________________________________________
    In a similar line of reasoning, the diagonal of the square that rises from the base to the right side is
      h(𝒙) = 4𝒙/3 + B = 0 … at 𝒙 = 25𝒂/9 so
      0 = ⁴⁄₃ × 25𝒂/9 + B
      B = -100𝒂/27 … so
      h(𝒙) = 4𝒙/3 - 100𝒂/27
      𝒔² = 400𝒂²/81 … thru lots of little algebra
    With that we can find where it intersects at g(𝒙), the equation for the right side of the large containing triangle.
      g(𝒙) = -4𝒙/3 + 16 (because must be 0 at [𝒙 = 12])
    Working through a lot of algebra setting [h(𝒙) = g(𝒙)], Icame up with
      𝒙 = 6 + 75𝒂/54
    Since this lower right triangle is SIMILAR to the △ABC overall one, which is isosceles, we know that
      𝒔² = (6 - 75𝒂/54)² + (⁴⁄₃)²(6 - 75𝒂/54)² … reduces to
      𝒔² = ²⁵⁄₉(6 - 75𝒂/54)² … thus also
      400𝒂²/81 = ²⁵⁄₉(6 - 75𝒂/54)² … which expands to
      441𝒂² - 48600𝒂 + 104976 = 0 … being quadratic has roots
      𝒂 = [ 108 or 2.2041 ]
    Clearly it cannot be the larger one, so 2.2041 ought to work.
      𝒔² = 400 × 2.2041² ÷ 81
      𝒔² = 23.9900
    Or about 24. Yay! HARD work.
    ⋅-⋅-⋅ Just saying, ⋅-⋅-⋅
    ⋅-=≡ GoatGuy ✓ ≡=-⋅

  • @laxmikatta1774
    @laxmikatta1774 7 месяцев назад

    What is the meaning of your channel name sir??

    • @howardaltman7212
      @howardaltman7212 7 месяцев назад

      Great name, isn't it. Nothing beyond Algebra 1 and Geometry on the Pre-Math channel.

  • @hanswust6972
    @hanswust6972 7 месяцев назад

    I used Sin α = 0.8 to solve the side of the square EF = x.
    CF / AC = EF / AF
    8 / 10 = X / 6
    X = 4.8
    AREA = 4.8^2 = 23.04
    What is wrong with my approach?

    • @mattemodin666
      @mattemodin666 7 месяцев назад

      I'm curious as well, because I got same answer (only difference was getting cos  - cosines Law).

    • @mauriciosahady
      @mauriciosahady 7 месяцев назад +1

      CF is not the height. F is not the middle point. AF = 6,122

    • @mattemodin666
      @mattemodin666 7 месяцев назад +1

      @@mauriciosahady Thanks. Now I can see my mistake: it's similar, not same triangles.

  • @pinoytutor
    @pinoytutor 7 месяцев назад +3

    This topic is for advanced students so please avoid over explaining how to add the fractions. Just give the answer straight away. That will make the content more relevant

  • @user-mj7ir5de6j
    @user-mj7ir5de6j 7 месяцев назад +2

    Say allaho akbar

    • @PreMath
      @PreMath  7 месяцев назад

      Thanks❤️