Approximate Integral of cos(x^2)

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SUMMARY

The forum discussion focuses on calculating the error involved in the trapezoidal and midpoint methods for the integral ∫cos(x^2) from 0 to 1 with n=8. The error bounds are defined by the equations |Et|<= k(b-a)^3/(12n^2) and |Em|<=k(b-a)^3/(24n^2). The second derivative of the function, f''(x) = -4x^2cos(x^2), is evaluated at x=1, yielding f''(1) = -3.844, confirming that the second derivative is negative, which is relevant for error estimation. The maximum value of |f''(x)| over the interval [0, 1] is crucial for determining k in the error formulas.

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  • Understanding of numerical integration methods, specifically trapezoidal and midpoint methods.
  • Familiarity with error analysis in numerical methods.
  • Knowledge of calculus, particularly derivatives and their significance in error estimation.
  • Ability to evaluate functions and their derivatives, specifically f(x) = cos(x^2).
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  • Research the application of the trapezoidal rule and midpoint rule in numerical integration.
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sugarxsweet
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Homework Statement


I am having issues figuring out the error involved in the trapezoidal and midpoint methods for ∫cos(x^2) from 0 to 1 with n=8


Homework Equations


|Et|<= k(b-a)^3/(12n^2)
|Em|<=k(b-a)^3/(24n^2)


The Attempt at a Solution



f(x)=cos(x^2)
f'(x)=-2xsin(x^2)
f''(x)=-4x^2cos(x^2)

f''(1) = -3.844

Is it right given that f''(1) is negative? Just wanted to make sure! Thanks
 
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sugarxsweet said:

Homework Statement


I am having issues figuring out the error involved in the trapezoidal and midpoint methods for ∫cos(x^2) from 0 to 1 with n=8


Homework Equations


|Et|<= k(b-a)^3/(12n^2)
|Em|<=k(b-a)^3/(24n^2)


The Attempt at a Solution



f(x)=cos(x^2)
f'(x)=-2xsin(x^2)
f''(x)=-4x^2cos(x^2)

f''(1) = -3.844

Is it right given that f''(1) is negative? Just wanted to make sure! Thanks

It doesn't matter: k = max{|f''(x)|: 0 ≤ x ≤ 1}.

RGV
 

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