Question

sin(x)=sin(2x)

Answer 1

Hint let x = 2x

Answer 2

And obviously, as you know the sine function is periodic. If you know the period of the function then you can figure out other values of x that will work as well.

Answer 3

yeah, if sines of 2 numbers are equal to each other, then isn't it right to say that the numbers themselves are also equal ?