Question 641428
sin(x + y) - sin(x - y) = 2cos(x)sin(y)


sin(x)cos(y) + cos(x)sin(y) - (sin(x)cos(y) - cos(x)sin(y)) = 2cos(x)sin(y)


sin(x)cos(y) + cos(x)sin(y) - sin(x)cos(y) + cos(x)sin(y) = 2cos(x)sin(y)


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


So that verifies the identity