Question

cosπ/3-tanπ/4+3/4tan2π/6-sinπ/6+cos2π/6+sin3π/2计算

Answer 1

=1/2 -1 +3√3/4 -1/2+1/2 -1
=(3√3 -6)/4

Answer 2

cosπ/3-tanπ/4+3/4tan2π/6-sinπ/6+cos2π/6+sin3π/2
=1/2-1+3√3/4-1/2+1/2-1
=3√3/4-3/2

追问

（3）已知tana=-3/4，求sina，cosa，cota的值
（4）已知cosa=0.68,求sina，tana，cota的值（计算结果保留两个有效数字）。
我要过程..