Vector Components and Finding the Angle

1. Sep 18, 2006

Soaring Crane

Let the angle theta be the angle that the vector A makes with the +x-axis, measured counterclockwise from that axis. Find the angle theta for a vector that has the following components:

A_x = -4.50m
A_y = -3.30m

Using the calculator, I got arctan(-3.30m/-4.50 m) = 36.25 degrees.

However, this answer is wrong. I know the angle is supposed to be counterclockwise from +x-axis, but I thought the signs canceled out. What is the correct way of determining the angle?

Thanks.

Last edited: Sep 19, 2006
2. Sep 18, 2006

6Stang7

where is an angle theta equal to 0 at? think about how the problem stated the increase in theta.

did you draw a picture?

3. Sep 19, 2006

Soaring Crane

Well, I drew vector A in quadrant 3 and subtracted the angle from 270 (270 - 36.25 = 234), but that answer is wrong.

Last edited: Sep 19, 2006
4. Sep 19, 2006

Hootenanny

Staff Emeritus