Question

How do you evaluate `sin^-1(sin((9pi)/10))`?

Answer 1

`(9pi)/10`

Explanation:

Successive operations with f and its inverse `f^(-1)`, either way, on

an operand, returns the operand as the result.

Explicitly, if y = f(x), then `f^(-1)f(x)=x and f f^(-1)y=y`.

Here, `f = sin, f^(-1)=sin^(-1)` and the operand is `(9pi)/10`.

So, `sin^(-1)sin ((9pi)/10) = (9pi)/10`.