Question

Given tan∅=4/3 and π<∅<(3π)/2; find cos2∅

Answer 1

Answer:

$cos(2\theta)=-\frac{7}{25}$

Step-by-step explanation:

we are given

$tan(\theta)=\frac{4}{3}$

Firstly, we will draw triangle

Since, angle lies in third quadrant

so,

$sin(\theta)=-\frac{4}{5}$

$cos(\theta)=-\frac{3}{5}$

now, we can sue formula

$cos(2\theta)=cos^2(\theta)-sin^2(\theta)$

now, we can plug values

$cos(2\theta)=(-\frac{3}{5})^2-(-\frac{4}{5})^2$

we can simplify it

$cos(2\theta)=-\frac{7}{25}$