已知cosα=1/7,cos(α-β)=13/14,且0<β<α<π/2,求sinβ
已知sin(5π-α)=根号2×cos[(2÷7)+β]和根号3×cos(-α)=根号2×cos(π+α),且0<α<π
已知0<α<π/2,且3sinα=4cosα求(sin^2α+2sinαcosα)/(3cos^2α-1)求cos^2α
已知COS(2α-β)=-11/14 SIN(α-2β)=4倍根号3/7 且π/4<α<π/2,0<β<π/4 求COS
已知sinα - sinβ=1/3 cosα + cosβ=1/7 0 < α,β < π/2,求sin(α+β)/2的
已知sinα+sinβ+sinγ=0,cosα+cosβ+cosγ=0.求cos(β
已知cos(π/2-α)-2cosα=sinπ,且cosα<0,则sinα的值为?
已知cos(π/3+α)=-3/5 ,sin(2π/3-β)=5/13,且0<α<π/2<β<π,求cos(β-α).
1、已知cos(π/3+α)= -3/5,sin(2π/3-β)=3/15,且0<α<π/2<β<π,求cos(β-α)
已知cosα=1/7,cos(α+β)=-11/14,且α、β∈(0,2/Π),求cosβ的值
已知sinα+sinβ=14,cosα+cosβ=13
已知α、β≠kπ+π2(k∈Z),且sinθ+cosθ=2sinα , sinθcosθ=sin
已知sinα×cosα=1/8 且π/4 <α<π/2 则cosα-sinα的值