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Jul
6
answered Is $\infty = \frac{1}{0}$?
Jul
5
comment Axiom of Choice and finite sets
"How do I choose such an x?" is often a good question if you're writing a computer program. But in mathematics, if you want to use the existence of $x$ then tautologically you need only a proof that $x$ exists.
Jul
5
awarded  Nice Answer
Jul
5
revised Understanding matrices.
added 202 characters in body
Jul
4
answered Understanding matrices.
Jul
4
comment Understanding matrices.
That code isn't right. Maybe you mean newX = cos(angle)*oldX-....
Jul
4
revised What is the geometric meaning of this integral?
added 2 characters in body
Jul
3
answered What is the geometric meaning of this integral?
Jul
1
revised Second derivative of discrete function
This isn't discrete mathematics
Jul
1
suggested approved edit on Second derivative of discrete function
Jul
1
awarded  Enthusiast
Jun
30
comment Given a histogram, programatically, how do I find the normal distributions that comprise it?
See en.wikipedia.org/wiki/…
Jun
30
comment What's wrong with having the same variable in the integrand as in the limits?
@QiaochuYuan You point to the real issue. In principle $\int_0^x(\int_0^xx^3dx)x^4dx$ is unambiguous. But mathematicians like the abuse of notation that allows them to write what you just wrote and they find it worthwhile to sacrifice $\alpha$-equivalence to get it. (See en.wikipedia.org/wiki/Lambda_calculus#Alpha_equivalence .) I suspect that modern mathematics students with some computing experience may have slightly different ideas of what's reasonable.
Jun
28
answered Fibonacci Calculation using a larger matrix
Jun
27
revised Ways to study mathematics while commuting
added 243 characters in body
Jun
27
answered Ways to study mathematics while commuting
Jun
27
comment Topologies on n-manifolds
Do you mean other topologies? Or other topologies on $n$-manifolds? If the former then you'll find you need to understand the compact-open topology if you intend to study homotopy theory. en.wikipedia.org/wiki/Compact-open_topology
Jun
25
comment Where does this unit vector come from?
There is a sphere here :-) The reason is that unit vectors are vectors of length 1, i.e. if you place the vector's tail at the origin its head lies on the unit sphere. So, in disguise, your question is "where does the vector $F_1$ meet a unit sphere?"
Jun
25
comment Is this mathematically correct?
Well $v_1/v_2=13/15$ but $r_1/r_2=1$ for row 1. But suppose there are errors up to 10% in your voltage measurements, so, eg. $v_1$ is actually 2.8 and $v_2$ is actually 2.8, etc., then the relationship might hold exactly.
Jun
25
comment Is this mathematically correct?
The relationship doesn't hold exactly. But if your voltage measurements are only accurate to 0.5V, say, then it is possible that the relationship holds. That's why experimenters give error bars when they publish results. Do you have some estimates of your uncertainty?