Question

Question #9e7a0

Answer 1

`x=0,1.77,4.51,2pi`

Explanation:

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

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

`sec^2x+4secx-5=0`

`a=secx`

`a^2+4a-5=0`

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

`a=1 or a=-5`

`secx=1 or secx=-5`

`cosx=1 or -1/5`

`x=arccos(1)=0 and 2pi`
or
`x=arccos(-1/5)~~1.77^c or ~4.51^c`