设arctan 根号(x^2-1)=a
arcsin1/x=b
则sina=根号(x^2-1)/x cosa=1/x
sinb=1/x cosb=根号(x^2-1)/x
sin(a+b)=sinacosb+cosasinb=根号(x^2-1)/x *根号(x^2-1)/x+1/x*1/x=1=sinπ/2
(a+b)=π/2