f(x) = 2(cosx)^2 + 根号3sin2x -1
= 根号3sin2x + cos2x
= 2sin(2x + π/6)
令2kπ + π/2 < 2x + π/6 < 2kπ + 3π/2
解得递减区间是
(kπ+ π/6 ,kπ + 2π/3)
f(x) = 2(cosx)^2 + 根号3sin2x -1
= 根号3sin2x + cos2x
= 2sin(2x + π/6)
令2kπ + π/2 < 2x + π/6 < 2kπ + 3π/2
解得递减区间是
(kπ+ π/6 ,kπ + 2π/3)