Question

If I reduce the evaluation of a trigonomic function, what is the evaluation of the same fucntion at it's reference angle? sin 2.5 and cos 2.5!

Answer 1

The result will be the same in absolute value (can differ by a \(\pm\) sometimes). The reference angle will always output a positive number, so see whether your sine, cosine, or whatever is positive or negative in the quadrant of the original angle and then change the sign accordingy.