### Home > PC3 > Chapter 11 > Lesson 11.1.4 > Problem11-70

11-70.

Evaluate each of the following trigonometric expressions. Give exact answers.

1. $\sin( \frac { 3 \pi } { 8 } )$

$\sin\left(\frac{3\pi/4}{2}\right)$

1. $\cos( \frac { x } { 2 } )$ if $\cos\left(x\right)=\frac{1}{6},\ \pi \leq x \leq 2\pi$

$\pm\sqrt{\frac{1+\cos(x)}{2}}=\pm\sqrt{\frac{1+1/6}{2}}$ if $\cos(x) = \frac { 1 } { 6 }$$π ≤ x < 2π$