急求大神帮我求y=sin2x+cos2x的最小正周期,最大最小值,
5个回答

y=sin2x+cos2x

=√2(sin2x*√2/2+cos2x*√2/2)

=√2sin(2x+π/4)

最小正周期T=2π/w=2π/2=π

∵-1≤sin(2x+π/4)≤1

∴-√2≤√2sin(2x+π/4)≤√2

最大值为√2

最小值为-√2

令-π/2+2kπ≤2x+π/4≤π/2+2kπ

-3π/4+2kπ≤2x≤π/4+2kπ

-3π/8+kπ≤x≤π/8+2kπ

所以单调递增区间为{x l -3π/8+kπ≤x≤π/8+2kπ}(k∈Z)

令π/2+2kπ≤2x+π/4≤3π/2+2kπ

π/4+2kπ≤2x≤5π/4+2kπ

π/8+kπ≤x≤5π/8+2kπ

所以单调递减区间为{x l π/8+kπ≤x≤5π/8+2kπ}(k∈Z)