Originally Posted by

**ebaines** Correct - that's not so hard!

The only "tricks" to remember are:

(a) __Always__ convert the angles sso that they ar measured counter-clockwise from the positive x axis. So the angle of the 40 N force is really 180-80 = 100 degrees, and the 15 N force is 180+ 45 = 225 degrees.

(b) In taking the arc tan a positive result is either quadrant 1 or 3, and a negative result is either quadrant 2 or 4. So you need to look at the signs of Fx_total and Fy_total to figure out which quadrant. Here since both Fx_total and Fy_total are positive (right?) that means the resultant is in quadrant 1, and you are measuring from the positive x axis.

Excellent. Thanks for the help. Our tutor expects us to know all this without being taught, so the help is appreciated. The explanations he does give complicate something that is really quite simple and still don't help to solve problems, for instance I've never been taught how work out which way the resultant force should go until now!