- #1
Nikitin
- 735
- 27
Hi, I really need some help here.. Vectors remind me why I hate geomtery.
problem 1: Prove that |UxV|2 = |U|2+|V|2 - (U*V)2
How can I prove that these two are equal without spending 1 hour using algebra? Maybe there is some geometry quirk that I'm not seeing?
problem 2: We have two vectors A=[1,1,1] and B=[1,2,3]
Find a vector C so that AxB = AxC, where C =! B.
I tried using algebra on this but I just ended up with crazy expressions for Cx, Cy and Cz where each of them were dependent on the others.
So.. Is there some other way? All help is appreciated =)
problem 1: Prove that |UxV|2 = |U|2+|V|2 - (U*V)2
How can I prove that these two are equal without spending 1 hour using algebra? Maybe there is some geometry quirk that I'm not seeing?
problem 2: We have two vectors A=[1,1,1] and B=[1,2,3]
Find a vector C so that AxB = AxC, where C =! B.
I tried using algebra on this but I just ended up with crazy expressions for Cx, Cy and Cz where each of them were dependent on the others.
So.. Is there some other way? All help is appreciated =)
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