Use periodic properties of the trigonometric functions to find the exact value of the expression.
-$\tan \frac { 21 \pi } { 4 }$
A) 1
B) $\sqrt { 3 }$
C) $\frac { \sqrt { 3 } } { 3 }$
D) $- 1$

Question

Quizplus · Accepted Answer

The period of the tangent function is $\pi$, so $\tan \frac{21\pi}{4} = \tan (\frac{20\pi}{4} + \frac{\pi}{4}) = \tan (5\pi + \frac{\pi}{4}) = \tan \frac{\pi}{4}$, which equals 1.

Use Periodic Properties of the Trigonometric Functions to Find the Exact