Common Math Mistake 7

Degrees vs. Radians
Most trig classes that I’ve seen taught tend to concentrate on doing things in degrees. I suppose that this is because it’s easier for the students to visualize, but the reality is that almost all of calculus is done in radians and students too often come out of a trig class ill prepared to deal with all the radians in a calculus class.
You simply must get used to doing everything in radians in a calculus class. If you are
asked to evaluate cos (x) at x =10 we are asking you to use 10 radians not 10 degrees!
The answers are very, very different! Consider the following,

cos (10) = - 0.839071529076 in radians
cos (10) = 0.984807753012 in degrees

You’ll notice that they aren’t even the same sign!
So, be careful and make sure that you always use radians when dealing with trig functions in a trig class.