Question

How do you evaluate `tan 90`?

Answer 1

`tan90^@` is undefined.

Explanation:

![http://www.coolmath.com/precalculus-review-calculus-intro/precalculus-trigonometry/28-the-unit-circle-01]()

Since the angle is `90^@`, there will be a unit circle instead of a special triangle. Any point at `90^@` can be described as (`0, y`). However, to make things easier to understand, we will use a radius of `1`, meaning the height (`y`) is also `1`. The point will be (`0, 1`).

`tan90^@=y/x`
`tan90^@=1/0`
`tan90^@=`undefined

`tan90^@` is undefined because you can't divide `1` by nothing.

This is like saying:

`1` divided by `0` is `color(red)? rArr color(red)?` multiplied by `0` is `1`

Nothing multiplied by `0` will give an answer of `1`, so the answer is undefined.