Let me preface this by saying I have no idea what a force factor is, but you're not getting the whole formula. There is a function on your calculator which is called the inverse sine.
which if you have a TI-89 or something similar, can be found by either pressing the "second" button and then the sine function, which will look something like
* -1
sin (
on the display screen. Or another way to find it is by going into the calculator's catalog and finding
arcsin(
A personal note from the engineering nerd... the inverse sine function is NOT the same as the inverse *of* the sine function. Meaning:
* -1 (....space filler....) __
1__
sin (x) does NOT equal sin(x)
Also, make sure your calculator is in degree mode, not radian. (the setting can most likely be found under "mode" on your calculator)
...or you could spare doing the hand work and just use this: (this is just the search link, you have to find it for your OS)
http://www.bing.com/search?q=coaster+ca ... orm=OSDSRC