Hi, I'm really having problems with this question, can someone please help me. Thank-you!

Question

Algebraically solve for 0<phaeta<2pi, 2cos^2 phaeta-7 cos phaeta +3=0

Answer 1

allow me to use x instead of 'phaeta' for ease of typing, so
cos^2 x - 7cosx + 3 = 0
(2cosx - 1)(cosx - 3) = 0
cosx = 1/2 or cosx = 3, the latter not possible.
if cosx=1/2,then x = pi/3 or 5pi/3 (60º or 300º)