# Tagged Questions

Questions on the use of numerical functions NIntegrate and NDSolve.

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### How to solve in principle such coupled ODEs

One example for coupled ODEs from the Mathemtica help center reads ...
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### NDSolve: Improperly assigned stepsize

This is not a question which I estimate is aided in answering by providing complete code, which is excessively long. I ran an NDSolve[] at ...
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### NDSolve and piecewise functions

I'm trying to use NDSolve on a Pde for a function that is made up of several pretty complicated functions, most of which are themselves functions of an underlying piecewise function. When I try to ...
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### Approximation of definite integral by parabolas

This question is related to Trapezoid approximation to definite integral. As promised, I am now asking about how to draw an approximation of integrals by parabolas. I tried to modify MarcoB's code, ...
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### Trapezoid approximation to definite integral

This question is related to Graphically approximating the area under a curve as a sum of rectangular regions. I now was trying to adapt the code by MarcoB to get the approximation of the integral by ...
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### NDSolve Step Size Effectively Zero

I'm trying to solve a PDE for a function of 2 variables. The most accurate parameterizations of this equation are very unwieldy and involve numerous piecewise elements, and so right now I'm trying to ...
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### How to solve algebra equations containing integration and parameters?

I'm trying to solve two nonlinear algebra equations for two unknown parameters, U and Tf. Since some terms in these equations contain integration, and the integration also contains U and Tf. The main ...
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### In NMinimize, how can I efficiently handle NIntegrate errors for non-integrable functions?

I am using NMinimize to find parameters that minimise the integral of a function in the least squares sense: ...
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### Seconde Derivatives of an integral [closed]

$$g(x) = \int_{-\infty}^{x^2/2} e^{-(x^2+1)t^2}dt\,.$$ Trouble calculating the first and the second derivative of this function.
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### Strange behaviour of integrals with Cos, Sin, and Exp

During the study of the problem How to solve this integration? I have discovered a strange behaviour of some integrals. I would consider it a bug. ...