I denote x-prime a nd y-prime by a and b respectively.

We have

where

compare real and imaginary parts, you will get it.

ii. By expressing x and y in terms of polar coordinates, demonstrate that the following identities hold for all angles A and B:

a) sin (A+B) = sinA cosB + cosA sinB

b) cos (A+B) = cosA cosB - sinA sinB

and

multiply the above two equation and compare real and imaginary parts

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