Wednesday, May 13, 2015

Find out the solutions of the equation sin 2x = 2 sin x, in the interval (0,2pi).

sin 2x= 2 sin x


2 sin x cos x= 2sin x


2 sin x cos x - 2 sin x=0


2 sin x (cos x -1)=0


It's a two factors multiplication, and the result is 0 when one of these two factors is 0, too.


2 sin x =0, sin x=0


x=arcsin 0


x=0 or x=pi


cos x - 1=0


cos x=1


x=+/-arccos 1


x=0, x=pi

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