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by **woodson_28** » Thu Aug 30, 2007 6:12 pm

I tried to make this as easy to understand as possible. There are 5 questions, anybody remember how to do this stuff?

limx → 0 ( -2 + cos 5x + cos^2 5x − 4 sin 5x ) / (-2x ) =

limx → 0 ( -5 − 2 cos 5x + 7 cos^2 5x − sin 5x ) / (5x^2 − 5x ) =

limx → 0 (3^(2x) - 1) / (x + 3) =

limx → 0+ (1 + x )^(1/(2x)) =

limx → 0 (3^x - 1) / x =

5 questions, I have pretty much forgotten how to do this crap. Any help on any of the five would be greatly appreciated. Thanx

by **SniperShot** » Thu Aug 30, 2007 6:56 pm

All of those are very simple limits. You're trying to find the limit of X as it approaches 0 in each of those 5 problems. I'd say pay attention in class and learn how to use your graphing calculator.

For those 5 problems I'd use substitution. When X is approaching 0 half your values in those equations become 0. :-D

Having others do your homework hurts you big time in the long run.

by CC » Thu Aug 30, 2007 7:51 pm

Boom!
http://mathforum.org/library/drmath/drmath.college.html

I dominate most of my courses and practical math, but abstract math like calculus I need to work a little harder to succeed at.

by **Santacruzer** » Thu Aug 30, 2007 7:56 pm

Your mom bought you that computer in your room for you to do your homework, not us.

:-b

jk

Been too long for me. I can't help ya.

by **joshyboy72** » Sat Sep 01, 2007 7:45 pm

Yep just subsitute 0 for X. Or if you're lazy like me.. just graph it, and go the graph screen and calc the value for when X equals 0. From the look of a couple of those, it might be undefined. But there could still be a limit for those.

by **Plindsey88** » Sat Sep 01, 2007 10:59 pm

Trying to remember back to my high school days...

I think these are problems solved by L'Hopital's Rule, which states something like lim (f(x)/g(x)) = lim (f'(x)/g'(x)).

Right?

by **Mercer Boy** » Fri Sep 07, 2007 9:25 am

How can you substitute 0 for x in those? They would have division by 0 which is illegal... :-?

It has been about 8 years since I did those, so I really don't remember where to start. You probably have to get x out of the denominator somehow? Like synthetic division? Maybe L'Hospital's rule like Plindsey said (yes I know I spelled it wrong...that's how I always said it)? I think you do the derivative of it and figure it out that way.

Maybe since it's just approaching zero it's not illegal to divide by it. Must be nice doing those on graphing calculators these days. :*)

Oh, another thought...if you can turn some of the trig functions into whole numbers it could help. There are all sorts of them in your calc book most likely. In any event, you better post the answers. ;-D

by **knapplc** » Fri Sep 07, 2007 10:01 am

Mercer Boy wrote:How can you substitute 0 for x in those? They would have division by 0 which is illegal...

It has been about 8 years since I did those, so I really don't remember where to start. You probably have to get x out of the denominator somehow? Like synthetic division? Maybe L'Hospital's rule like Plindsey said (yes I know I spelled it wrong...that's how I always said it)? I think you do the derivative of it and figure it out that way.

Maybe since it's just approaching zero it's not illegal to divide by it. Must be nice doing those on graphing calculators these days.

Oh, another thought...if you can turn some of the trig functions into whole numbers it could help. There are all sorts of them in your calc book most likely. In any event, you better post the answers.

Yeah, but who enforces those laws? The Math Cops?

by **treat24** » Fri Sep 07, 2007 10:08 am

knapplc wrote:
Mercer Boy wrote:How can you substitute 0 for x in those? They would have division by 0 which is illegal...

It has been about 8 years since I did those, so I really don't remember where to start. You probably have to get x out of the denominator somehow? Like synthetic division? Maybe L'Hospital's rule like Plindsey said (yes I know I spelled it wrong...that's how I always said it)? I think you do the derivative of it and figure it out that way.

Maybe since it's just approaching zero it's not illegal to divide by it. Must be nice doing those on graphing calculators these days.

Oh, another thought...if you can turn some of the trig functions into whole numbers it could help. There are all sorts of them in your calc book most likely. In any event, you better post the answers.

Yeah, but who enforces those laws? The Math Cops?

math cops these days are much better than the ones when we went to school knapp: