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2020-06-09 13:40:33 +0100 | asked a question | Assume expression to be noninteger Hello! How to assume expression to be an integer? I try to do some symbolic integration while Sage asks to provide additional info about expression. MWE: gives:
How to assume that
Thanks! |

2017-11-19 12:44:06 +0100 | commented answer | Substitution of subexpression Interesting and confusing.. Why do I have to include w in subexpression? |

2017-11-19 12:11:50 +0100 | asked a question | Substitution of subexpression Hi! My task is to derive some expression and then find subexpressions in it and substitute. In details I need to find derivative of psi and then substitute expressions back. The way I found this derivative looks ugly but I suppose it's easier to do substitution in such form of expression. $-2{\left(w x \cos\left(t w\right) + w y \sin\left(t w\right)\right)} {\left(\frac{\pi \alpha \cos\left(\frac{\pi y_{2}}{a}\right) \sin\left(\frac{2 \pi x_{2}}{a}\right)}{a^{2}} + \frac{2 \pi \beta \cos\left(\frac{2 \pi y_{2}}{a}\right) \sin\left(\frac{\pi x_{2}}{a}\right)}{a^{2}}\right)}+$ $+2{\left(w y \cos\left(t w\right) - w x \sin\left(t w\right)\right)} {\left(\frac{\pi \beta \cos\left(\frac{\pi x_{2}}{a}\right) \sin\left(\frac{2 \pi y_{2}}{a}\right)}{a^{2}} + \frac{2 \pi \alpha \cos\left(\frac{2\pi x_{2}}{a}\right) \sin\left(\frac{\pi y_{2}}{a}\right)}{a^{2}}\right)}$ Then I need to substitute x $\$0 {\left(x \cos\left(t w\right) + y \sin\left(t w\right)\right)} + \$1 {\left(y \cos\left(t w\right) - x \sin\left(t w\right)\right)}$ which is looks pretty the same but somehow don't match: gives None. Could someone explain what is going on or maybe I should use something else? |

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