Question

what is the value of cos(infinity)

Answer 1

i don't know how to get it, but http://www.wolframalpha.com/input/?i=cos%28infinity%29

Answer 2

It's undefined, but is in the range of [-1,1]

Answer 3

can u explain it please....??

Answer 4

Infinity is not a number; you can't take the cosine of something that is not a number.
If you take the limit of cos(x) as x approaches infinity, you'll essentially be taking the cosine of a ridiculously large number, but you won't know what that number actually is.

Answer 5

You can also try taking the limit of cos(1/x) as x goes to 0, and the cosine function will fluctuate rapidly between -1 and 1, but won't have a defined value at x=0.