Question

How do you use a calculator to evaluate `cot1.35`?

Answer 1

Rewrite `cot(1.35)` as `1/tan(1.35)`.

`cot(1.35) ~~ 0.22`

Explanation:

Very few calculators have the cotangent function, but they do have the sine, cosine, and tangent functions. If we can rewrite cotangent as some combination of these functions, we will be able to evaluate it.

Recall the reciprocal identities.

`csc(x) = 1/sin(x)`

`sec(x) = 1/cos(x)`

`color(red)(cot(x) = 1/tan(x))`

And applying this identity,

`cot(1.35)`

`= 1/tan(1.35)`

`~~ 1/4.46`

`~~ 0.22`