Science Bowl Question

W) cos(2x) = 2 cos(x)[cosine of 2x equals 2 cosine of x]

X) sin(2x) = 2 sin(x) cos(x) [sine of 2 x equals 2 sine of x cosine of x]

Y) cos(x + y) = cos(x) + cos(y) [cosine of the quantity x plus y equals cosine of x plus cosine of y]

Z) sin(x - y) = sin(x) - sin(y) [sine of the quantity x minus y equals sine of x minus sine of y]