课时知能训练
一、选择题
1.记cos(-80°)=k,那么tan 100°=( )
A.1-k2k B.-1-k2k
C.k1-k2 D.-k1-k2
2.(2012•泉州模拟)已知f(α)=sinπ-α•cos2π-αcos-π-α•tanπ-α,则f(-31π3)的值为( )
A.12 B.-12 C.32 D.-32
3.(2012•东莞模拟)已知tan θ=2,则sin2θ+sin θcos θ-2cos2θ=( )
A.-43 B.54 C.-34 D.45
4.若cos α+2sin α=-5,则tan α=( )
A.12 B.2 C.-12 D.-2
5.已知sin θ=2cos θ,则sinπ2+θ-cosπ-θsinπ2-θ-sinπ-θ=( )
A.2 B.-2 C.0 D.23