Calculus 3: Vector Calculus in 3-D (21of 35) Magnitude of the Cross Product of 2 Vectors

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In this video I find the magnitude=? of the cross product of vectors AxB=? given A=3i-2j-5k and B=i+4j-4k using 2 method. Method 1: |AxB|=|C|=ABsin(theta)=?, Method 2: using matrices.
Next video in the series can be seen at:
• Calculus 3: Vector Cal...

[@Decidiovs_OG]

why did it change from sin to cos? And Vice Versa?

[@Koolb-wn4er]

It's because he was using the dot product formula when solving for theta. Then when he was solving for the cross product, he switched back.

[@mclovelacenoether]

Thank you for your video!

[@MichelvanBiezen]

You are welcome!

[@safartalib5414]

why did it change sin for cos??😐

[@mikefaraday1720]

There were two formulae involved. A different formula involving cos and dot product was used to find theta before substituting theta into the cross product formula involving sin to find the magnitude of the cross product. It may be late for you but hopes this helps somebody.

[@carlbenedictsolomon5894]

Thank you sir!

[@MichelvanBiezen]

You are welcome!

[@humpty2360]

Thank you

[@MichelvanBiezen]

Welcome!

[@cyrusdotillos3498]

Sir I have a vector product given the problem is my answer using the vector product is in negative but using the magnitude equation which is ABsintheta is positive but still they ended up the same answer, they only differ in sign. Is it possible sir or the way I solve was wrong

[@MichelvanBiezen]

A x B = - B x A The sign is only relevant if you want the direction of the vector product. When you use AB sin(theta), then you are calculating the magnitude of the vector product, and magnitudes of vectors can only be positive.

[@cyrusdotillos3498]

thank you sir

[@divyamtyagi]

Sir please give the Proof of cross product formula

[@hectorlml1257]

Hi teacher If I get a result close to the other, is it correct or is there something to correct? Greetings.

[@MichelvanBiezen]

It is probably correct. There may be some round-off errors.

[@hectorlml1257]

@@MichelvanBiezen Thank you so much!

[@agharenovweavwerosuo1916]

Sir why did you change it from sin -cos

[@MichelvanBiezen]

Not sure what you mean by: "from sin - cos"

[@MichelvanBiezen]

We use the dot product to find the angle between two vectors (since A dot B = | A| * |B| cos (theta) )

[@mtv280]

How did you get 7,14,28?

[@MichelvanBiezen]

That was shown in the videos before this one in the playlist: Calculus 3: Vector Calculus in 3-D (19 of 35) How to Calculate the Cross Product of 2 Vectors?

[@mtv280]

@@MichelvanBiezen ok thank you

[@battulavivek8550]

Very good

[@MichelvanBiezen]

Very good

[@raiton_gamer]

Arigato sir

[@MichelvanBiezen]

You are welcome.

[@Tantheta.30]

Jee wale like karo😂