求cos2x+sin2x的单调增区间
问题描述：
求cos2x+sin2x的单调增区间
答得好再附赠
答
令f(x)=cos2x+sin2xf¹(x)=-2sin2x+2cos2x=2(cos2x-sin2x)=2√2cos(2x+π/4)≥0∴2kπ-π/2≤2x+π/4≤2kπ+π/2kπ-3π/8≤x≤kπ+π/8 k∈Z所以cos2x+sin2x的单调增区间为 [kπ-3π/8,kπ+π/8] k∈Z...