Why Does My Calculus Integral Result in Undefined?

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    Calculus
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Discussion Overview

The discussion revolves around a calculus problem involving the integral of an exponential function, specifically the expression .0065 times the integral of e to the power of (-.0139(t-48) squared). Participants are exploring the challenges in finding the integral, particularly when applying the chain rule, and discussing the nature of the solution, whether it can be expressed in elementary functions or requires numerical methods.

Discussion Character

  • Debate/contested, Mathematical reasoning, Homework-related

Main Points Raised

  • One participant expresses confusion over obtaining an undefined result when attempting to apply the chain rule to the integral.
  • Another participant argues that there is no correct answer in terms of elementary functions for the integral in question.
  • A different participant notes that the integral \exp\left(-a(t-t_0)^2\right) does not have an elementary antiderivative but can be evaluated exactly if the limits extend to infinity.
  • Some participants suggest that the problem may involve numerical solutions or the error function, which is related to the integral but is not elementary.
  • Clarification is sought regarding the limits of integration, which are later identified as 48 to 60.
  • Several participants confirm arriving at a numerical approximation of the integral, specifically around .04664.
  • There is a suggestion that numerical integration methods could be a viable approach to solving the problem.

Areas of Agreement / Disagreement

Participants express differing views on whether the integral can be solved using elementary functions, with some asserting it cannot while others suggest numerical methods yield a solution. The discussion remains unresolved regarding the nature of the integral and the methods to approach it.

Contextual Notes

Participants note the problem is presented in a calculus textbook under the section for logarithmic and exponential integration, which raises questions about its classification and the expectations for solving it. There is also mention of potential confusion regarding the problem's presentation and the limits of integration.

whisperblade
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can anyone figure this out? i keep getting undefined somewhere but my teacher says there is a correct answer.

heres the problem.

.0065 times the integral of e to the (-.0139(t-48)squared) power.

i can't find the integral cause i get undefined when the chain rule is used to chain out the exponent.
 
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i don't think there is a correct answer. not with "elementary functions" anyway.
 
\exp\left(-a(t-t_0)^2\right) does not have an elementary antiderivative.
You can get an exact expression of the integral though if the limits of integration extend to infinity.

What are the limits of integration in your problem?
 
whisperblade said:
can anyone figure this out? i keep getting undefined somewhere but my teacher says there is a correct answer.

heres the problem.

.0065 times the integral of e to the (-.0139(t-48)squared) power.

i can't find the integral cause i get undefined when the chain rule is used to chain out the exponent.

Try graphing the equation. I believe the gaussian (bell - curve) is also this kind, for which the answer should then be 1. Not sure though.
 
Presumably you're looking for a numerical solution right? Otherwise the solution is the error function related which is not elementary.
 
well the thing is this is a problem in our calculus book in the section under logarithmic and exponential integration. which is weird. there is nothing else to the problem except what i have given here. the book asks for the answer to that probability equation and wants it as a percentage. while its great that i have the answer, i don't know how to get it because i get undefined
 
It might be a good idea to tell us what the problem actually is! The way you posed the problem originally, it was an indefinite integral but it appears that the problem gave specific limits.
 
i thought i gave the restrictions? it was from 48-60. that is why i was saying i get undefined from the chain rule. sorry for the confusion
 
Is the answer approximately .046641?
 
  • #10
Got that too: 0.04664079814
 
  • #11
yah! it is. how did u get that.
 
  • #12
whisperblade said:
yah! it is. how did u get that.
Numerical integration would definitely work.
 

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