Ditch the 2s in sin 2x and cos 2y
8.1 Express sin 2x as a product of single-angle trigonometric functions.
The expression sin 2x is described as a “double angle,” because the argument of the expression is 2x rather than simply x. The identity below allows you to rewrite the double-angle expression sin 2x as the product of two single-angle expressions.
sin 2x = 2 sin x cos x
8.2 Verify your answer to Problem 8.1 by applying the sum formula for sine.
Apply the sum formula for sine to expand sin 2x. Note that sin 2x = sin (x + x).
This formula comes from Problem 7.34.
8.3 Simplify the expression: .
Apply the double-angle ...