# Trig question

How do you go about finding the arctangent of an unfamiliar number. Example, arctan (-2)? I think it's in the direction of half-angles and double angels, but how do I get the angle to start with the formulas in the first place?

If x = arctan(-2), then tan(x) = -2. I don't think double or half-angle will help you for this problem. Sometimes you can figure out what x is, sometimes you can't without a calculator.

berkeman
Mentor
How do you go about finding the arctangent of an unfamiliar number. Example, arctan (-2)? I think it's in the direction of half-angles and double angels, but how do I get the angle to start with the formulas in the first place?