calculus
posted by Anonymous .
Find the xcoordinates 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 commaseparated 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