Solve 2cos(x)-sec(x)=1 for 0 (degrees) is less than or equal to x ,and x is greater than or equal to 180?

Answer 1

multiply by cos x to get

2 cos^2 x -1 = cos x
or 2 cos^2 x - cos x -1 = 0
or 2(cos x +1)(cos x -1 ) = 0


cos x = 1 => x= 0
2 cos x + 1 = 0 => cos x = -1/2 x = 5pi/3 or 7pi/3

Answer 2

2 cosx - 1 / cosx = 1
2 cos²x - 1 = cosx
2 cos²x - cosx - 1 = 0
(2 cosx + 1).(cosx - 1) = 0
cos x = - 1/2 , cosx = 1
x = 240° , 360° (as x is ≥ 180°)

Answer 3

errrr x = 0. because cos(0) = 1 and sec(0) = 1