f(x) = 2(sqrt(3)/2 cos(2x-Theta) - 1/2 sin(2x-theta)) = -2 sin (2x - theta - pi/6)
-theta - pi/6 = -pi/2
theta = pi/3
f(x) = -2cos2x
横坐标缩短为原来的2/3倍f(x') = -2cos3x'
向左平移π/18
f(x'+pi/18) = -2cos(3x'+pi/6)
g(x) = 1-cos(3x+pi/6)
g(x) - 2m - 1 = 0
m = (g(x)-1)/2
0.25