I am using a TI-89 calculator. The highest level of math I've taken is high school calculus. I was playing around with infinity, and entered cos(infinity), which returned sin(infinity). Why is this? I don't understand limits incredibly well, but I know that the range of the sine and cosine functions fluctuates between 1 and -1. I guess you could also say that their domain is the same, as -infinity to infinity? It is approaching infinity along the x axis, but does not approach anything along the y-axis?
Can anyone shed more light on this? Thanks.