posted by Anonymous .
Find the x-coordinates of all points on the curve
f(x) = sin 2x − 2 sin x
at which the tangent line is horizontal. (Enter your answers as a comma-separated list. Use n to represent any integer.)
tangent is horizontal when f'(x) = 0
f'(x) = 2cos2x - 2cosx
f'(x) = 0 when x = 2k*pi or 2k*pi +/- 2pi/3
for all integers k