1.sin163°sin223°+sin253°sin313°=___ 2.已知 α,β均为锐角,且cosα=4/5,cos(α+β )=-16/65,那么cosβ=_______3.已知 α,β均为锐角,且sinα=根号五/5,cosβ=根号十,那么α-β=_________4.已知 α,β∈(0,π/2),sinα-sinβ=-1/2,
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![1.sin163°sin223°+sin253°sin313°=___ 2.已知 α,β均为锐角,且cosα=4/5,cos(α+β )=-16/65,那么cosβ=_______3.已知 α,β均为锐角,且sinα=根号五/5,cosβ=根号十,那么α-β=_________4.已知 α,β∈(0,π/2),sinα-sinβ=-1/2,](/uploads/image/z/3579625-1-5.jpg?t=1.sin163%C2%B0sin223%C2%B0%2Bsin253%C2%B0sin313%C2%B0%3D___+2.%E5%B7%B2%E7%9F%A5+%CE%B1%2C%CE%B2%E5%9D%87%E4%B8%BA%E9%94%90%E8%A7%92%2C%E4%B8%94cos%CE%B1%3D4%2F5%2Ccos%EF%BC%88%CE%B1%2B%CE%B2+%EF%BC%89%3D-16%2F65%2C%E9%82%A3%E4%B9%88cos%CE%B2%3D_______3.%E5%B7%B2%E7%9F%A5+%CE%B1%2C%CE%B2%E5%9D%87%E4%B8%BA%E9%94%90%E8%A7%92%2C%E4%B8%94sin%CE%B1%3D%E6%A0%B9%E5%8F%B7%E4%BA%94%2F5%2Ccos%CE%B2%3D%E6%A0%B9%E5%8F%B7%E5%8D%81%2C%E9%82%A3%E4%B9%88%CE%B1-%CE%B2%3D_________4.%E5%B7%B2%E7%9F%A5+%CE%B1%2C%CE%B2%E2%88%88%280%2C%CF%80%2F2%29%2Csin%CE%B1-sin%CE%B2%3D-1%2F2%2C)
1.sin163°sin223°+sin253°sin313°=___ 2.已知 α,β均为锐角,且cosα=4/5,cos(α+β )=-16/65,那么cosβ=_______3.已知 α,β均为锐角,且sinα=根号五/5,cosβ=根号十,那么α-β=_________4.已知 α,β∈(0,π/2),sinα-sinβ=-1/2,
1.sin163°sin223°+sin253°sin313°=___
2.已知 α,β均为锐角,且cosα=4/5,cos(α+β )=-16/65,那么cosβ=_______
3.已知 α,β均为锐角,且sinα=根号五/5,cosβ=根号十,那么α-β=_________
4.已知 α,β∈(0,π/2),sinα-sinβ=-1/2,cosα-cosβ=1/2,那么sin(α-β)=________
5.在△ABC中,sin2A=2/3,则sinA+cosA=______
6.已知cos2θ=根号二/3,则sin四次方θ+cos四次方θ的值为____
怎么才能学好这些东西呀,公式都混在一块,乱死了==
1.sin163°sin223°+sin253°sin313°=___ 2.已知 α,β均为锐角,且cosα=4/5,cos(α+β )=-16/65,那么cosβ=_______3.已知 α,β均为锐角,且sinα=根号五/5,cosβ=根号十,那么α-β=_________4.已知 α,β∈(0,π/2),sinα-sinβ=-1/2,
1.sin163°sin223°+sin253°sin313°=_-sin17°sin43°+cos17°cos43°
=cos(17°+43°)=cos60°=1/2__
2.已知 α,β均为锐角,且cosα=4/5,cos(α+β )=-16/65,那么
cosβ=cos[(α+β)-α]=cos(a+β)cosa+sin(a+β)sina=-16/65*4/5+56/65*3/5=8/25
3.已知 α,β均为锐角,且sinα=根号五/5,cosβ=根号十,那么α-β=_________
sin(α-β)=sinacosβ-cosasinβ=根号五/5* 根号十 /10-2根号五/5* 3根号十 /10=-√2/2
α-β=-45°
4.已知 α,β∈(0,π/2),sinα-sinβ=-1/2,cosα-cosβ=1/2,那么sin(α-β)=________
sinα-sinβ=-1/2 平方 sin^2α-2sinαsinβ+sin^2β=1/4
cosα-cosβ=1/2 平方 cos^2α-2cosαcosβ+cos^2β=1/4 相加
2-2(cosαcosβ+sinαsinβ)=1/2
2cos(α-β)=3/4
cos(α-β)=3/8 sinα-sinβ=-1/2 a