Question #9e7a0

1 Answer
Feb 26, 2018

x=0,1.77,4.51,2pix=0,1.77,4.51,2π

Explanation:

First, we will use the identity tan^2x=sec^2x-1tan2x=sec2x1

sec^2x-1+4secx=4sec2x1+4secx=4

sec^2x+4secx-5=0sec2x+4secx5=0

a=secxa=secx

a^2+4a-5=0a2+4a5=0

(a-1)(a+5)=0(a1)(a+5)=0

a=1 or a=-5a=1ora=5

secx=1 or secx=-5secx=1orsecx=5

cosx=1 or -1/5cosx=1or15

x=arccos(1)=0 and 2pix=arccos(1)=0and2π
or
x=arccos(-1/5)~~1.77^c or ~4.51^cx=arccos(15)1.77cor~4.51c