# Magnitude and angle counterclockwise from the + x direction

1. Jan 28, 2012

### bearbratz

1. The problem statement, all variables and given/known data
Express your answer in part (a) in terms of magnitude and angle counterclockwise from the + x direction.
Vector = -25.3i-1.2j

2. Relevant equations

3. The attempt at a solution
Arctan(-1.2/25.3)=2.72
This is wrong... but I have no idea how to fix it.

2. Jan 28, 2012

### technicolour1

Re: Vectors

Since tan is a trig function that repeats every 90deg, some consideration must be put into the signs of x and y. Since x and y are both negative, 180deg must be added to the value calculated to obtain the correct value. Likewise, if y is negative and x is positive, 270deg must be added. If x is negative and y is positive, 90deg must be added. This is shown when looking at a plot of the tan function. To confirm this answer (182.72), plug it into tan and see if it gives you your y/x ratio.

3. Jan 28, 2012

### bearbratz

Re: Vectors

Thank you very much that worked.