1. ## vector problem

prove that u = cos(theta)i-sin(theta)j and v = sin(theta)i+cos(theta)j are unit vectors for any angle theta.

thanks, i appriciate that.

2. Originally Posted by runrunrun
prove that u = cos(theta)i-sin(theta)j and v = sin(theta)i+cos(theta)j are unit vectors for any angle theta.

thanks, i appriciate that.
Elementary,
$\displaystyle ||\b{u}||=\cos^2 \theta+(-\sin \theta )^2=\cos^2 \theta +\sin^2\theta =1$.

You do the other one.

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# Is ? (Sin theata i cos j ) is unit vector

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