Chapter SH, Problem 13.19EP

To determine

To find:

The each expression into trigonometric form

Answer to Problem 13.19EP

The exact value is $\theta ={120}^0$

Explanation of Solution

Given:

  $\text{2cos}\theta +\text{1=}\text{0}$

Concept used:

Trigonometric ratios: - Atrigonometric ratio are the ratios between edges of a right triangle.

Calculation:

Trigonometric ratio is

  $\begin{array}{l}\text{2cos}\theta +\text{1=}\text{0}\\ 2\cos \theta =-1\\ \cos \theta =-\frac{\text{1}}{2}\\ \theta =\frac{2\pi }{3}\\ \theta ={120}^0\end{array}$