y = 2 sin2x cos2xy = sin4xT = 2π/4 = π/2ymin = -1 at 4x = 2kπ - π/2ymax = 1 at 4x = 2kπ + π/2递增区间[kπ/2 - π/8,kπ/2 + π/8],k∈Z------------------------------------------------------------y...第一题前面没有2的，化简后是1/2sin4x请问能把第一题再写一遍吗？我会采纳的好吧，我会了