# Limits question

• Oct 3rd 2011, 06:39 PM
Dustin10
Limits question
I know how to solve the more basic limits, but I'm stuck here. How would I got about solving this one?

Lim (2x^2+Cosx)/(3x^2+x-1+e^-2)
x-->2
• Oct 3rd 2011, 06:45 PM
pickslides
Re: Limits question
Where are you stuck? What have you tried?

What does a direct substitution produce?
• Oct 3rd 2011, 06:51 PM
Dustin10
Re: Limits question
I tried directly putting in 2 but the answer it produced was wrong. So basically I'm just stuck on what to try next cause my professor is crap at explaining himself.
• Oct 3rd 2011, 06:55 PM
Prove It
Re: Limits question
Quote:

Originally Posted by Dustin10
I tried directly putting in 2 but the answer it produced was wrong. So basically I'm just stuck on what to try next cause my professor is crap at explaining himself.

Or rather your simplification was wrong, because substituting x = 2 is the correct procedure. Why not show what you did and we can point out your mistake, rather than defaming your poor professor?
• Oct 3rd 2011, 07:10 PM
Dustin10
Re: Limits question
I'm sure I'm making some mistakes, but following a professor who confuses himself and has to re-do solutions cause he makes mistakes on a regular basis makes it tough to pick up on the trickier application of stuff :P but here's what I tried. I'm pretty sure the e is what's making me do this incorrectly.

(2(2)^2+Cos(2))/(3(2)^2+2-1+e^(-2))

(8+1.00)/(12+2-1+0.14)= 9.00/13.14 which was incorrect.

I then tried to move the e^(-x) to the numerator to make the power positive but just like I figured that was wrong too. Just not exactly sure where my mistakes are :/
• Oct 3rd 2011, 07:12 PM
Prove It
Re: Limits question
Quote:

Originally Posted by Dustin10
I'm sure I'm making some mistakes, but following a professor who confuses himself and has to re-do solutions cause he makes mistakes on a regular basis makes it tough to pick up on the trickier application of stuff :P but here's what I tried. I'm pretty sure the e is what's making me do this incorrectly.

(2(2)^2+Cos(2))/(3(2)^2+2-1+e^(-2))

(8+1.00)/(12+2-1+0.14)= 9.00/13.14 which was incorrect.

I then tried to move the e^(-x) to the numerator to make the power positive but just like I figured that was wrong too. Just not exactly sure where my mistakes are :/

cos(2) =/= 1
• Oct 3rd 2011, 07:19 PM
Dustin10
Re: Limits question
Quote:

Originally Posted by Prove It
cos(2) =/= 1

I was doing it on my calculator and getting 0.999390827 so I rounded to 1.00
• Oct 3rd 2011, 08:54 PM
mr fantastic
Re: Limits question
Quote:

Originally Posted by Dustin10
I was doing it on my calculator and getting 0.999390827 so I rounded to 1.00

It is NOT 2 degrees, it is 2 RADIANS. Change the mode of your calculator.