Solve `7 cos^(2)x+sin x cos x-3=0`.

Answer

`x=n pi +(3pi)/4 and x=k pi +"tan"^(-1) 4/3 (k, n in Z)`

Explanation

`7 cos^(2) x+sin x cos x-3=0`
Dividing by `cos^(2)x`, we get
`7+tan x-3 sec^(2) x=0`
or `7+tan x-3 (1+tan^(2) x)=0`
or `3 tan^(2) x-tan x-4 =0`
or `(tan x+1) (3 tan x-4)=0`
or `tan x=-1` and `tan x=4/3`
`rArr x=npi +(3pi)/4, n in Z`
and `x=kpi+tan^(-1) (4/3), k in Z`