Question

Question #c1993

Answer 1

Many calculators don't have a `sec^-1` button. So, if we want to evaluate `sec^-1(8)`, we'll have to rewrite it.

First, let:

`sec^-1(8)=theta`

Via the definition of inverse functions:

`8=sec(theta)`

Since secant and cosine are reciprocals:

`1/8=cos(theta)`

Then:

`cos^-1(1/8)=theta`

Thus:

`sec^-1(8)=cos^-1(1/8)`

Which can be plugged into a calculator.