有几道三角函数的问题麻烦做一下,急,200分

1.sin(arcsin(π))没有意义;因为π>1,超出了反正弦的定义域;
2.arcsin(cos(0))=arcsin1=π/2
3.sin^-1(sin(1/2))=1/2,
因为当-π/2≤x≤π/2,即x值落在反正弦的主值区间时arcsin(sinx)=x
4.cos^-1(cos(5π/4))=arccos(-√2/2)=(3π)/4
反余弦的主值区间是[0,π]
5.tan(cos^-1(x/5))
设α=cos^-1(x/5),α∈[0,π]则 cosα=x/5,sinα=√[1-(x/5)^2], tanα=[√(25-x^2]/x
即tan(cos^-1(x/5))==[√(25-x^2]/x
6.cos(sin^-1(x/√ 4+x^2))
设α=sin^-1(x/√ 4+x^2), α∈[-π/2,π/2],则sinα=x/√ 4+x^2, cosα=√(1-sin^2 α)=2/√(4+x^2)
即cos(sin^-1(x/√ 4+x^2))＝2/√(4+x^2)