Answer to Question #87408 in Trigonometry for Rena

Question

The expression cos-1 (3/5) has an infinite number of values. True or False? http://prntscr.com/n65c1h

Answer 1

Trigonometric functions are periodic, so their inverse functions are unambiguous. Unambiguousness is obtained by the considering of the range of principal values ($[0, \pi]$ for $\cos ^{-1}$). So expression $\cos ^{-1}(3/5)$ has a single value at the range of principal values $[0, \pi]$.

Answer: False.