# How do you calculate # [tan^-1(-1) + cos^-1(-4/5)]#?

##### 1 Answer

May 15, 2016

#### Explanation:

It is anticlockwise rotation for angles. So, negative angles do not appear.

Let

Then,

So, a is in the 2nd or 4th quadrant.

The solutions in

Let

Then,

So, a is in the 2nd or 3rd quadrant.

The solutions in

The given expression is

If negative angles are used like #[-180^o, 180^0] for the range of

separate solutions, instead, the results would change, accordingly.