# Homework Help: Angular Motion

1. Jun 10, 2004

### zillea

this should be a simple question, but I am just not getting the right answer. I need to change 25 degrees to radians. I know, that 360 degrees = 2pi radians, but I am not getting the right answer.
thanks for the help

2. Jun 10, 2004

### Gza

multiply 25 degrees by $$\frac {\pi}{180}$$.

Just look at the units to remember how to do this. (number in radians and degrees are technically unitless, but use radians and degrees as the units)

3. Jun 11, 2004

### BobG

Just to expand ...

You were on the right track. The only possible way I can see you getting the wrong answer is if you got your denominator and numerator swapped.

If you want to convert from degrees to radians, you want to get rid of the degrees. That means the degrees has to be in the denominator so it cancels out.

If you want to convert from degrees to radians, you want to get rid of the radians. That means the radians has to be in the denominator.

Since $$\frac{2\pi}{360} = \frac{\pi}{180}$$

and $$\frac{360}{2\pi} = \frac{180}{\pi}$$

Most people just multiply degrees by $$\frac{\pi}{180}$$
or radians by $$\frac{180}{\pi}$$

If you happen to have a good slide rule, it's even easier. Set the cursor over the number of degrees on the D scale, and move the slide until the r mark on the C scale is under the hairline. Look below the C index and you have your number of radians. (This is basically the same as dividing the number of degrees by 57.2957795, which happens to equal 180/pi).