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deedsy
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Homework Statement
A and B are two unit vectors in the x-y plane.
A = <cos(a), sin(a)>
B = <cos(b), sin(b)>
I need to derive the trig identity:
sin(a-b) = sin(a) cos(b) - sin(b) cos (a)
I'm told to do it using the properties of the cross product A x B
Homework Equations
A x B = |A||B| sinθ , where θ is the angle between the two vectors
The Attempt at a Solution
Well, |A|=|B|=1 *unit vectors
sinθ = sin(a-b) *for a > b
A x B = cos(a)sin(b) - cos(b)sin(a)
Putting this together, I get:
sin(a-b) = cos(a)sin(b) - cos(b)sin(a)
I can't figure out what I did wrong?