Making a definite integral equal and indefinite integral?

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Discussion Overview

The discussion revolves around the relationship between definite and indefinite integrals, specifically exploring whether it is possible to choose limits for a definite integral such that it equals an indefinite integral with a constant of integration set to zero. Participants examine the behavior of integrals using different graphing tools.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant notes that their calculator sketches indefinite integrals assuming the constant of integration is zero, while another tool requires definite integrals.
  • Another participant explains that if the definite integral is defined as ##F(x)=\int_a^x f(t)dt##, it will resemble the indefinite integral ##G=\int f(x)dx##, but shifted downwards by the value of ##G(a)##.
  • A further contribution suggests that if the lower limit 'a' is set to an x-intercept of the indefinite integral, the resulting sketch of the definite integral could align with that of the indefinite integral without any shift.
  • Two participants express agreement with the idea that setting 'a' to an x-intercept should work to achieve the desired outcome.

Areas of Agreement / Disagreement

Participants generally agree on the approach of setting 'a' to an x-intercept to align the definite integral with the indefinite integral, but the discussion does not resolve all aspects of the relationship between these integrals.

Contextual Notes

The discussion does not address potential limitations or assumptions regarding the choice of 'a' or the implications of shifting the integral graphs.

Saracen Rue
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I have a calculator which allows me to sketch indefinite integrals - it assumes c = 0. However, when I try to use Desmos Online Graphing Calculator, it won't let me do this with it's integral function. It keeps trying to make me use definite integrals.

I know that ∫(a,b,f(x)dx = F(a) - F(b), so I was wondering if it's possible to define a and b so that the resulting definite integral equals the indefinite integral (where c = 0)
 
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How does it sketch the definite integrals? If it sketches the curve of ##F(x)## vs ##x## where ##F(x)## is defined as:
$$F(x)=\int_a^x f(t)dt$$
then the sketch will be exactly the same as that of an indefinite integral ##G=\int f(x)dx## with zero integration constant, except shifted downwards by ##G(a)##.
 
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andrewkirk said:
How does it sketch the definite integrals? If it sketches the curve of ##F(x)## vs ##x## where ##F(x)## is defined as:
$$F(x)=\int_a^x f(t)dt$$
then the sketch will be exactly the same as that of an indefinite integral ##G=\int f(x)dx## with zero integration constant, except shifted downwards by ##G(a)##.
So if I make a equal to a x-intercept of the indefinite integral of f(x), then
$$F(x)=\int_a^x f(t)dt$$
With no shift?
 
Yes, that should work.
 
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andrewkirk said:
Yes, that should work.
Thank you! :)
 

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