Chapter 4.5, Problem 50E

Solution

To calculate: The approximate solution for the equation $4\cos x=\tan x$ in the interval $-\pi <x<\pi$ .

The approximate solution for the equation $4\cos x=\tan x$ in the interval $-\pi <x<\pi$ is $x\approx 1.082$ or $x\approx 2.060$ .

Given information:

The equation $4\cos x=\tan x$ in the interval $-\pi <x<\pi$ .

Formula used :

Use the graphical method to find the solution.

Calculation:

Consider the equation $4\cos x=\tan x$ ,

Subtract $\tan x$ from both sides.

  $\begin{array}{c}4\cos x-\tan x=\tan x-\tan x\\ 4\cos x-\tan x=0\end{array}$

Use TI-83 calculator to find the solution.

Put the calculator in RADIAN mode.

Put the equation as $y=4\cos x-\tan x$ .

Set up the window for the variables.

  

Graph the function.

  

  

It can be seen that the graph attains value of $y=0$ at $x\approx 1.082$ or $x\approx 2.060$ .

Thus, the approximate solution for the equation $4\cos x=\tan x$ in the interval $-\pi <x<\pi$ is $x\approx 1.082$ or $x\approx 2.060$ .