Chapter 13 - The Trigonometric Functions - 13.1 Definitions of the Trigonometric Functions - 13.1 Exercises - Page 678: 1

$$\frac{\pi }{3}{\text{radians}}$$

$$\eqalign{ & {\text{We know that }}{{\text{1}}^ \circ } = \frac{\pi }{{180}}{\text{radians}}{\text{. So}}{\text{,}} \cr & {60^ \circ } = 60\left( {\frac{\pi }{{180}}} \right){\text{radians}} \cr & {\text{Multiplying}} \cr & {60^ \circ } = \frac{{60\pi }}{{180}}{\text{radians}} \cr & {60^ \circ } = \frac{\pi }{3}{\text{radians}} \cr} $$