it was jst on a booklet that we got from out teacher.....i think he may hav made it up himself.......
but yeh thts all the information that we get sooo......i wasnt sure!!......also for some reason my calculator reckons that it is undefined after about x=29......but this didnt really make sense.......so i just put R down as the domain...cause that is the answer to most trig functions.....!....but yeh dont know why it doesnt continue....i think the values stuffed the calculator up.....because if you sub in 50 for x it refuses to give you a proper answer......bit strange...might just ask my teacher next class........unless someone can help furthermore!!!
Let's think what happens when you sub in x = 50.
cos(4e^50). Hmm. 2^50 < e^50 < 3^50. 2 is roughly 10^0.3 and 3 is roughly 10^0.5 (very, very roughly)
So e^50 is between 10^15 and 10^25. Yikes.
One really important problem you have for this, practically, is because the calculator will have an error in the value of e (it has to use a finite number of decimal places), its value for e^x will also have an error, and for larger x values, this error becomes so significant that your value for cos(4e^x) isn't reliable anymore.