Pythagorean theorem

sin² + cos² = 1

Periodicity properties

Therefore the sine and cosine functions are periodic with period 2.

sin(x + 2) = sinx

cos(x + 2) = cosx

Other properties

sin(-) = - sin(), the sine function is odd.

cos(-) = cos(), the cosine function is even.

Addition theorem

sin(x+y) = sinx cosy + cosx siny

cos(x+y) = cosx cosy - sinxsiny

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