Weird trig equation (1 Viewer)

[jxballistic]

My friend showed me this equation which i couldn't do:

[cos(x)]^2 +7sin(x)cos(x) = 3 (sorry I dont know how to use latex)

I tried using double angle formula but I cant find a solution

can someone please show me how to do it?
thanks!

 

[nightweaver066]

Divide through by (cosx)^2, then change (secx)^2 to 1 + (tanx)^2.

 

[Beaconite]

Divide through by (cosx)^2, then change (secx)^2 to 1 + (tanx)^2.

+1

 

[jxballistic]

Divide through by (cosx)^2, then change (secx)^2 to 1 + (tanx)^2.

I got a quadratic equation and got these answers :x= 63*26*, 18*26*, 243*26*, 198*26* (nearest min)
is this right?

 

[Sy123]

Just plug into the calculator