Integral: Evaluate x^3 sin (t^2) dt

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SUMMARY

The integral to evaluate is ∫(x to x^3) sin(t^2) dt, which requires the application of the second fundamental theorem of calculus. The correct approach involves differentiating the integral, yielding the expression 3x^2 sin(x^6) - sin(x^2). However, the solution also involves the Fresnel integral, represented as sqrt(π/2)[S(sqrt(2/π)x^3) - S(sqrt(2/π)x)], where S(x) denotes the Fresnel integral of sin(t^2) dt from 0 to x. The discussion clarifies that the problem is not about evaluating the integral directly but rather finding its derivative.

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Homework Statement



Evaluate the integral (upper limit x^3 and lower limit x) sin (t^2) dt

Homework Equations





The Attempt at a Solution



I tried using the second fundamental theorem to do: 3x^2 sin (x^6) - sin (x^2). I'm not sure if this is right though.
 
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Is it some kind of a double integral?
 
what do you mean by double integral?
 
You have to use Fresnel integrals. Integrating the sin(t^2) by hand is not easy. What class is this for?
 
It's AP Calculus AB.
 
That question shouldn't be there, are you sure you read the problem right? could it have been (sin(t))^2 instead?The answer to the problem posted is as follows:

sqrt(Pi/2)[(S(sqrt(2/Pi)*x^3)-S(sqrt(2/Pi)*x)], where S(x) is the Fresnel integral of sin(t^2)dt from 0 to x.
 
I think they want the derivative not to evaluate the actual integral. Can I use the second fundamental theorem then?
 
Would you type in the instructions for the problem? I am not entirely sure what they are asking.
 
Frostbytez said:
I think they want the derivative not to evaluate the actual integral. Can I use the second fundamental theorem then?

The question does ask for the derivative of that integral, yes? And yes, you can use a fundamental theorem. And yes, you did it correctly.
 
  • #10
Frostbytez said:

Homework Statement



Evaluate the integral (upper limit x^3 and lower limit x) sin (t^2) dt

Homework Equations





The Attempt at a Solution



I tried using the second fundamental theorem to do: 3x^2 sin (x^6) - sin (x^2). I'm not sure if this is right though.

====

Yeah, I think that you are just over-complicating this... what is the derivative of
y = (-1/(t^2))cos(t^2) ...

Okay, the derviative of that is the integrand of your problem.
evalulating y from the top and bottom (of the integral domain) yields:
(-1/x^6)cos(x^6) +(1/x^2)cos(x^2)
 
  • #11
brydustin said:
====

Yeah, I think that you are just over-complicating this... what is the derivative of
y = (-1/(t^2))cos(t^2) ...

Okay, the derviative of that is the integrand of your problem.
evalulating y from the top and bottom (of the integral domain) yields:
(-1/x^6)cos(x^6) +(1/x^2)cos(x^2)

Wrong. The derivative of that is DEFINITELY not sin(t^2).
 

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