Hi sry for the previous double post, below is another porblem i faced:

given: 0 <= x < pi ; 0 <= y; < pi

...

sin^2x = sin^2y

(sinx + siny )( sinx - siny ) = 0

thus, how to get from above equation to form below 2 statements?

x = y+2pi( k ) //where is the pi & k come from?

x = -y+2pi( k )

Thank You!