If 1+cos² thetha =5/4. Find thetha

Answer 1

1+cos² thetha =5/4
cos^2 Ø = 5/4-1 = 1/4
cosØ = ±1/2

angle in standard position is 30°
but since cosØ is ±, Ø could be in any of the four quadrants

Ø = 30°, 150°, 210°, 330°
or
Ø = π/6, 5π/6, 7π/6, 11π/6