题目

已知sin(x+5π)=3/5,则sinx
化简：cos(x-π/2)/sin(x+5π/2)·sin(x-2π)·cos(2π-x)=
已知sinα=2根号5/5,α∈(π/2,π)则tanα=

提问时间：2021-03-30

答案

1,sin(x+5π)=-sinx=3/5,则sinx=-3/5
2,cos(x-π/2)/sin(x+5π/2)·sin(x-2π)·cos(2π-x)=sinx/cosx·sinx·cosx=sin²x
3,由α∈(π/2,π),sinα=2√5/5,cosα=-√5/5
tanα=-2
>.