# Tagged Questions

Questions related to memory devices that help learners recall larger pieces of information, especially in the form of lists like characteristics, steps, stages, parts.

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### How can I remember whether finite or countable cartesian product of countable set is countable

I always forget this result Is cartesian product of countable set countable under finite or countable cartesian products? Is there a good way to remember this? Like a proof sketch where the ...
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### Index notation of tensors and mnemonics

I've been trying to learn to manipulate tensors but I've got probably too comfortable with all the matrices in my Linear Algebra course, that it gets really difficult beyond rank-3 tensors. So, ...
Specific question: how can I improve on mentally performing calculations like these : $$(78-59)\times23-8\%\times(270+130)$$ [2\text{digit}+-2\text{digit}]\times2\text{digit}+-x\%\text{of}[3\text{...
The centroid of a region bounded by two curves is given by: $\bar{x} = \frac{1}{A}\int_a^b{x\left[f(x)-g(x)\right]dx}$ \$ \bar{y} = \frac{1}{A}\int_a^b{\left[\frac{(f(x)+g(x)}{2}(f(x)-g(x))\right]...