How is it that the top becomes the bottom?, my textbook says the 1/2nd are simple(im lost), the third uses the identities $\displaystyle sin^2t=\frac{1-cos2t}{2}$ & $\displaystyle cos^2t=\frac{1+cos2t}{2}$, the last one uses the Pythagorean identity $\displaystyle sin^2t+cos^2t=1$, the last two seem doable what are the first two? I don't see how the 1/8 becomes 1/16 to start. Edit:ignore thumbnail, added new picture