How do you find sin(tan1(a3))?

1 Answer
Sep 27, 2016

sin(tan1(a3))=aa2+9

Explanation:

Note that the range of tan1(y) is (π2,π2).

If θ(π2,π2) then cosθ>0.

If a3>0 then consider a right angled triangle with sides a3, 1 and a29+1

We find:

sin(tan1(a3))=a3a29+1=aa2+9

This identity continues to hold for a3<0 since sinθ and tanθ are odd functions.

It also holds for a=9 since sin(tan1(0))=sin(0)=0