Solve the equation sin 2 x º − cos x º = 0 in the interval 0 ≤ x ≤ 180.
I have taken it down to 2sin(x)cos(x)-cos(x) = 0
sin2x - cosx = 0
2sinx cos x - cosx = 0 factor out cosx
cosx [ 2sinx - 1] = 0 set each factor to 0
cosx = 0 and this happens at 180°
2sinx - 1 = 0 add 1 to both sides
2sinx = 1 divide by 2
sinx = 1/2 and this happens at 30° and at 150°
Actually, cosx = 0 at 90, not 180
the sinx is right though
