- #1

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I had to solve without the aid of a calculator:

2cos(x) = sin(2x)

What I did was perform the following substitution:

2cos(x) = 2sin(x)cos(x)

I then cancelled and got:

sin (x) = 1

For 0 to 3pi,

I got two answers, pi/2 and 5pi/2.

I did not get one of the answers. Why?

What did I do wrong?

Thanks!