# Magnitude and angles of a force

1. Aug 31, 2011

### IHave

1. The problem statement, all variables and given/known data
a force is given by F= 20i - 60j + 90k N. Find its magnitude and the angles it forms with the coordinate axis.

2. Relevant equations
F = magnitude of F times the unit vector
magnitude is square root (Fx squared + Fy squared + Fz squared)
and the unit vector can be written as (cos(theta)x)i + (cos(theta)y)j + (cos(theta)z)k
x for x component
y for y component
z for z component

to find the angle of the x component: inverse cosine of Fx/magnitude

3. The attempt at a solution
For the magnitude I got 110
for the angles with respect to x, y, z: 79.5, 123.1, 35.1

please tell me if i did something wrong! thanks

2. Aug 31, 2011

### rock.freak667

That should be correct.

3. Sep 1, 2011

### PeterO

Agree. All looks good.

4. Sep 2, 2011

### Lobezno

If a textbook or something gives a different answer, it's possible the angle is in another measurement, for example radians.