3sec^2x-5secx-2=0

Question

3sec²x-5secx-2=0

Answer 1

Let u = sec x

 

Then solve 3u² -5u - 2 = 0 (by factorinbg):  (3u  + 1)(u - 2) = 0

 

u = 2  i.e. sec x = 2  so cos x = ½.  (u cannot equal -1/3).

 

Finish this up!