cosα=2根号5/5 cosβ=根号10/10 α,β∈(0,π/2)求α-β=π-4
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cosα=2根号5/5 cosβ=根号10/10 α,β∈(0,π/2)求α-β=π-4
α,β∈(0,π/2)
cosα=2根号5/5 =2/根号5,sinα=根号[1-(2根号5/5)^2=1/根号5
cosβ=根号10/10=1/根号10 ,sinβ=根号[1-(根号10/10)^2]=3/根号10
osα/cosβ=(2根号5/5)/(根号10/10)=2根号>1
cosα>cosβ
α<β
cos(β-α)=cosβcosα+sinβsinα
=2/根号5*1/根号10+3/根号10*1/根号5
=根号2/5+3根号2/10
=5根号2/10
=根号2/2
∴β-α=π/4
α-β=-π/4
cosα=2根号5/5 =2/根号5,sinα=根号[1-(2根号5/5)^2=1/根号5
cosβ=根号10/10=1/根号10 ,sinβ=根号[1-(根号10/10)^2]=3/根号10
osα/cosβ=(2根号5/5)/(根号10/10)=2根号>1
cosα>cosβ
α<β
cos(β-α)=cosβcosα+sinβsinα
=2/根号5*1/根号10+3/根号10*1/根号5
=根号2/5+3根号2/10
=5根号2/10
=根号2/2
∴β-α=π/4
α-β=-π/4
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