f(x) = 2(sqrt(3)/2 cos(2x-Theta) - 1/2 sin(2x-theta)) = -2 sin (2x - theta - pi/6)-theta - pi/6 = -pi/2theta = pi/3f(x) = -2cos2x横坐标缩短为原来的2/3倍f(x') = -2cos3x'向左平移π/18f(x'+pi/18) = -2cos...