# Tagged Questions

For questions about symbolic computation, as opposed to numerical computations.

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### Issue with symbolic summation [duplicate]

Here is the sum: $$\sum_{j=0}^{n-1}r^{a+b}\cos^a\left(\frac{2\pi j}{n}+t\right)\sin^b\left(\frac{2\pi j}{n}+t\right)$$ Code: ...
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### Need help understanding the output of DSolve

I give Mathematica 10 the following command: DSolve[I D[P[x], {x, 2}] f[x] - (P'[x])^2 f[x] + 2 I P'[x] f'[x] == 0, P, x] and I have the following output: ...
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### Can this expression be calculated symbolically?

I want to do definite integration of the following expression ...
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### Opportunity for ordering mathematics through symbols

Hilbert came up with the idea of grounding all of mathematics in an a priori synthetic knowledge of symbols. Mathematica also pegs all mathematical operations down under a single roof aided by ...
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### Creating a Symbolic Singular Matrix

I am trying to differentiate an expression involving a matrix. When evaluating the input, Mathematica assumes the matrix is invertible, when it is not. How do I specify a symbolic singular matrix to ...
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### Expansion on sums of NonCommutativeMultiply

Following the MMa's documentations, the ExpandNCM[] function expands a**(b+c) without efforts (although I don't have very good ...
When I form a matrix of at least size $12 \times 12$ of second order polynomials in $w$ and I calculate the determinant of that, I get something that is a rational expression in $w$. Since the ...