Question 978579
{{{4cos^2(x)-4cos(x)-1=0}}}


discriminant is 16+4*4*1=32


{{{cos(x)=(4+- sqrt(32))/8}}}


{{{cos(x)=(4+- 4sqrt(2))/8}}}


{{{cos(x)=1/2+- (1/2)sqrt(2)}}}


cos(x) is 0.14645  or  0.85355
In quadrant 1 or quadrant 4.
(Arc whose cosine is....)


x is 81.6 degree or  31.4 degree, if in quadrant 1.