Chapter 14.3, Problem 13PPS

To determine

To calculate:Value of $\text{cos}{135}^{\circ }$

Answer to Problem 13PPS

  $-\frac{1}{\sqrt{2}}$

Explanation of Solution

Given information:

We know that, the given expression is $\text{cos}{135}^{\circ }$

Formula used:

  $\cos (\text{π}-\text{θ})=-\cos \text{θ},\cos {45}^{\circ }=\frac{1}{\sqrt{2}}.$

Calculation:

  $\begin{array}{l}\text{cos}{135}^{\circ }=\text{cos(}{180}^{\circ }-{45}^{\circ })\\ =\cos {45}^{\circ }\\ =\frac{1}{\sqrt{2}}.\end{array}$