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Greetings everyone!

I cannot get my HP 50g to find the limit as X approaches 0 when...

f(x)=(cos(x)-1+(1/2)*x^2)/x^4.

When I try to solve it on the calculator, regardless if in AOS or RPN, I always get the response "Insufficient order" from the calculator and puts a "?" as my answer. I know the problem has an answer because I solved it by hand. The answer is 1/24.

I have been able to find every limit I have encountered with my HP 50g until now so this is a very unexpected problem that surfaced. I have spent about 30 minutes trying to figure it out but came out with nothing. Therefore, I am hoping I can count on everyone's help here at the Museum, especially since I don't have anymore time to spend on this issue. (College. Need I say more?). Plus, it's getting rather frustrating but I just got to keep remembering that it's problems like these that makes me learn more about my HP 50g.

Thank you all so much in advance!

Hi!

The default order used by lim is less than 4, so it is too low for your example.
Put your function on stack level 3, 'X=0' on level 2, and the required order (4 at least) on level 1, then execute SERIES, instead of lim.

Best regards.

as suggested by Pascal:

'(COS(X)-1+X^2/2)/X^4' 'X=0' 4 SERIES --> { :Limit: '1/24' :Equiv: '1/24' :Expans: '1/24' :Remain: h } 'h=X'

so '1/24' is the answer

(02-23-2017 05:59 AM)Carsen Wrote: [ -> ]I cannot get my HP 50g to find the limit as X approaches 0 when...

f(x)=(cos(x)-1+(1/2)*x^2)/x^4.

When I try to solve it on the calculator, regardless if in AOS or RPN, I always get the response "Insufficient order" from the calculator and puts a "?" as my answer. I know the problem has an answer because I solved it by hand. The answer is 1/24.

A little off topic, but my HP Prime came out with the correct answer on both environments (Home and CAS), by just typing your function.
I know it's not a RPL machine and it doesn't have the 50G heritage, but it's a HP as well and highly oriented to the education market.

Pascal and Simone! Thanks so much! It worked perfectly the first time I tried it out. But now I have one more question in the functionality of the SERIES function. I do not understand the concept of the "order" that you put on level 1 of the stack before executing the function SERIES. How do I know what number of order to use? Keep in mind that I have not learned anything about Taylor Polynomials and I don't know too much about limits yet. I am only in Calculus 2.

Jebem. Yeah, I would LOVE to get a Prime mainly for it's touchscreen because it is so useful when graphing. But I am thinking of getting a HP 48gx first while I can because there are only so many of them left out there. Plus, I don't have too much of a budget for buying calculators...yet

Again, Thank you all for helping me out!