Question

Solving Trigonometric Equations

Answer 1

\[\cos (2x) = -1 \]

Answer 2

Getting confused by the 2x?

Just think of it as AN ANGLE, like theta. Maybe that will help.\[\large \cos \theta = -1\]If we wanted to solve for theta, we would just remember what special angle this corresponds to. It's pi right?\[\large \theta = \pi\]
So in our problem we have the same idea, but we'll have one more step after we get the reference angle because we want our answer in terms of x, not 2x.\[\large \cos(2x)=-1 \qquad \rightarrow \qquad 2x=\pi\]