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Just a nice old man


Dec
15
awarded  Caucus
Nov
12
answered Addition in linear vector spaces
Nov
9
comment Can a hyperbolic quadrilateral have 3 obtuse angles and 3 equal sides?
Not in hyperbolic space, but you can in elliptical space: just try to deform the second quadrilateral in elliptical geometry into the one you are imagining.
Oct
31
comment Why “a function continuous at only one point” is not an oxymoron?
a "connected" line? (even if it were of infinitesimal length)
Oct
31
comment question about continuity or discontinuity of a function
@DanZimm I posted my question here: math.stackexchange.com/questions/999320/…
Oct
31
asked Why “a function continuous at only one point” is not an oxymoron?
Oct
29
comment Find the value of k which makes f a density function.
It is actually the inverse of that number. The integral must be equal to 1.
Oct
29
comment question about continuity or discontinuity of a function
@DanZimm you are correct, thanks for the enlightenment! I still have trouble making sense of it. Continuity at only-one-point sounds like an oxymoron to my mind. Could it be that the classical definition of continuity fails to capture the concept of continuity for this pathological case? Or is it just me? I think I am going to post my own question about this.
Oct
29
revised question about continuity or discontinuity of a function
added 46 characters in body
Oct
28
comment Minimization of the difference between two functions
just write the equation between two arbitrary points on each line and minimize it (I assume you know calculus 101).
Oct
28
comment Show that $\int_{-1}^1f(t)dt = \sum_{i=1}^nw_if(a_i)$
Hailey, go back and read the calculus book again, please!
Oct
27
comment Numerical problem
The easiest method is a calculator, and the answer is 1003003001
Oct
27
comment Is this parametric equation correct?
I just tried to combine two parameters so that I would get the line for some values and the point for others, and luckily it was easy. I am pretty sure there must be a recipe for it, but I do not remember it, I left college a long time ago.
Oct
27
comment Is this parametric equation correct?
For what choices of s and t do you think your parametric equation gives (x,y,z)=(1,-2,4)? if there are no such s and t (there aren't), then the plane does not include that point.
Oct
27
revised Is this parametric equation correct?
added 33 characters in body
Oct
27
answered Is this parametric equation correct?
Oct
12
comment What is the dimension for this subspace?
1) is a plane, so dimension=2, 2) is a line (intersection of two planes), so dimension=1
Oct
11
comment Limit Question: lim theta---> 0 sin theta / 3 theta + tan theta: When you multiply 1/ cos theta by 1/ theta why doesn't your value change?
why should it? what rule would you be using? or what rule do you think was not done correctly in the example above? remember that theta is just a factor and you can chose where to "move" it, but you cannot put it inside the cosine function
Oct
11
comment Limit Question: lim theta---> 0 sin theta / 3 theta + tan theta: When you multiply 1/ cos theta by 1/ theta why doesn't your value change?
do you mean why not to put the theta inside the cosine function?
Oct
11
answered Point above or below the line