Question

Evaluate without using a calculator.

cos^-1(cos210degrees)

Answer 1

210 degree

Answer 2

\[f^-1(f(x)) = x \]

Answer 3

so its 210 degrees?

Answer 4

Inverse functions cancel each other out.

Answer 5

no that's not right here...
the range of inverse cosine is [0, 180degrees]

since cos(210) = cos(150), then \(\large cos^{-1}(210)=150 \)

Answer 6

Ah, good catch there, @ByteMe !