- 已知角a的终边经过点P(-3,4),求2six(π-a)•cos(2π-a)+1cos2a+sin(π2-a)• cos(3π2+a)的值.
- 设f(α)=2sinαcosα+cosα1+sin2α+cos(3π2+α)-sin2(π2+α)(1+2sinα≠0).(1)化简f(α).(2)求f(1°)•f(2°)•f(3°)•…•f(8...
- 代数式2cos10°-sin20°cos20°的值为( )A.2B.3C.1D.12
- 若cosα=13,cos(2π-α)•sin(π+α)sin(π2+α)•tan(3π-α)的值为______.
- (文)若 cos(π-A)=-12,则 sin(π2+A) 的值是( )A.32B.-32C.12D.-12
- 求sinπ12•sin5π12的值.
- 设3π4<θ<5π4,化简cosπ4sin(3π4-θ)[sin(π-θ)-sin(θ-π2)]sin(θ+π4).
- 已知α为锐角,且tanα=12,求sin2αcosα-sinαsin2αcos2α的值.
- sin(α+30°)-sin(α-30°)cosα的值为______.
- 已知△ABC中,tanA+B2=sinC,则∠C等于( )A.π6B.π4C.π3D.π2
- 已知sin(π-α)=m,(|m|≤1),则cos[2(π+α)]=______.
- 若sin(α-π)=35,则cos2α=( )A.1625B.1225C.925D.725
- 已知α∈(π2,π),且sinα=45,则sin(α+π2)-12cos(π+α)=______.
- 已知sin2α=23,则cos2(α+π4)=( )A.16B.13C.12D.23
- (Ⅰ)求证:sinx1-cosx=1+cosxsinx;(Ⅱ)化简:tan(3π-α)sin(π-α)sin(32π-α)+sin(2π-α)cos(α-7π2)sin(3π2+α)cos(2π+α).