find without tables or calculator.

Question

(1) sin^2 (22 1/2)- cos^2 (22 1/2)

(2) sin 60 cos 30 + sin 30 cos 60

(3) cos(90-y) = sin 56degree 47^i

Answer 1

(1) should remind you of the formula for cos 2x. It looks like -cos (2*22.5). You should know what cos 45 is.

(2) should remind you of the formula for sin (a + b)

(3) I have no idea what 47^i means, but cos (90-y) = sin y