sin2α=-24/25,α∈(-π/2,-π/4) 则sinα+cosα等于

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sin2α=-24/25,α∈(-π/2,-π/4)则sinα+cosα等于sin2α=-24/25,α∈(-π/2,-π/4)则sinα+cosα等于sin2α=-24/25,α∈(-π/2,-π/

sin2α=-24/25,α∈(-π/2,-π/4) 则sinα+cosα等于
sin2α=-24/25,α∈(-π/2,-π/4) 则sinα+cosα等于

sin2α=-24/25,α∈(-π/2,-π/4) 则sinα+cosα等于
(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

(sina+cosa)²
=sin²a+2sinacosa+cos²a
=1+sin2a
=1/25

∵α∈(-π/2,-π/4)
∴sina+cosa<0
∴sina+cosa=-1/5