Math.cos result WAY off

I have a function that takes an angle in degrees and converts it to radians. From there it takes the cosine of that angle and multiplies it by another number. The problem is the result of the Math.cos is way off.

The first line of code is this:
var theAngle = Math.abs(myAngle)*Math.PI/180;

myAngle is = -90. the result is that theAngle becomes 1.5707963267949.

From there I have this line of code:
var objAcc = grav * Math.cos(theAngle);

note that grav is set to .45. I've double checked in the debugger and theAngle is still equal to the above listed number. So, the result SHOULD be that objAcc should be equal to -1.5711675124992e-15. HOWEVER, it is actually being set to -1.72286501471525e-1. Is there something I don't know about working with Math.cos? If I run the function and put in the number itself instead of a variable it works out fine. It's just that when I have the variable in there it screws it up.
• 1. Re: Math.cos result WAY off
just below your definition of objAcc, what's the following reveal:

trace(grav);
trace(theAngle);
trace(objAcc);