Question

Rewrite the cosine function f(x)=cos(2x+π)
as a sine function. Show the steps you took to arrive at your answer.

Use the formula keypad when necessary.

(2 points)

Answer 1

Use the identity cos θ = sin(θ + π/2).

f(x) = cos(2x + π)
= sin((2x + π) + π/2)
= sin(2x + 3π/2)
= sin(2x + 3π/2 − 2π) (subtract 2π using periodicity)
= sin(2x − π/2).

So f(x) = sin(2x − π/2).