Question
Mon May 28, 2012 By: Anuj Kumar

Sir, I cannot understand the question given in the video espacially the last part of the following question.

Expert Reply
Tue May 29, 2012
To answer this, note that
sin(A+B) = sin A cos B + cos A sin B
sin(A-B) = sin A cos B - cos A sin B
cos(A+B) = cos A cos B - sin A sin B
cos(A-B) = cos A cos B + sin A sin B

Use A=pi/4 and x or y as B.

Note that sin(pi/4) = cos(pi/4) = 1/root(2) !!
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