sin2α=-24/25,α∈(-π/2,-π/4) 则sinα+cosα等于
问题描述：
sin2α=-24/25,α∈(-π/2,-π/4) 则sinα+cosα等于
答
(sinα+cosα)^2=(sina)^2+(cosa)^2+2sinacosa=1+2sinacosa
sin2α=2sinacosa=-24/25
(sinα+cosα)^2=1-24/25=1/25
α∈(-π/2,-π/4)
cosa>0,sina