sinα=3/5,α属于(-π/2,π/2),则cos(α+5π/4)等于多少?
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sinα=3/5,α属于(-π/2,π/2),则cos(α+5π/4)等于多少?
sinα=3/5,α属于(-π/2,π/2),则cos(α+5π/4)等于多少?
sinα=3/5,α属于(-π/2,π/2),则cos(α+5π/4)等于多少?
α属于(-π/2,π/2),
cosα>0
sin²α+cos²α=1
所以cosα=4/5
原式=cosαcos5π/4-sinαsin5π/4=-√2/10
-0.03