11,292 reputation
831
bio website mathsci.appstate.edu/~cookwj
location Boone, NC
age 34
visits member for 2 years, 7 months
seen 3 hours ago

Assist Prof. at Appalachian State University (in Western North Carolina)


9h
comment Radius of convergence of series
Just plug them in: $x=0$ and $ x=2$. One gives a divergent harmonic series. The other is a convergent alternating harmonic series.
1d
answered Radius of convergence of series
Apr
16
revised Finding surface integral of the paraboloid and disk
added 14 characters in body
Apr
14
comment Hyperplane avoiding some finite set
We have 1 dimension worth of cosets - which is an infinite set as long as our field is.
Apr
9
revised Different types of Convergence for a Series Function
switched to displaystyle fraction to be able to see it.
Apr
9
comment What is wrong with the limits of this triple integral?
Guys, the OP did state his region of integration: "under the paraboloid $z=4-x^2-y^2$ in the first octant".
Apr
9
answered What is wrong with the limits of this triple integral?
Apr
8
answered Hyperplane avoiding some finite set
Apr
8
comment Need desperate help with sketching functions/equations of functions of 2 and 3 variables
Yes. The two equations are equivalent so they yield the same graph.
Apr
7
comment Need desperate help with sketching functions/equations of functions of 2 and 3 variables
Sure. But you'll need to cut through with a "hyper-plane" instead of a plane -- that is -- something whose general formula is $ax+by+cz+dw=0$ for some constants $a,b,c,d$ (not all zero). So for example you could take the trace through $x=0$. This would yield the equation: $w=0^2+y^2+z^2=y^2+z^2$ which is a paraboloid. :)
Apr
7
answered Need desperate help with sketching functions/equations of functions of 2 and 3 variables
Apr
7
revised Need desperate help with sketching functions/equations of functions of 2 and 3 variables
added 36 characters in body
Apr
7
answered A couple of questions about a proof of the fact that a linear system has a non-trivial solution
Apr
7
revised Why $\langle y,x\rangle+\langle x,y\rangle=2\mathrm{Re}\langle x,y\rangle$? And the rules of using absolute value, inner production and norm?
added 292 characters in body
Apr
4
comment Proving that a set of polynomials P2 is a subspace of P3
Sure. If $f(1)=0$ then $f(x) = g(x) \cdot (x-1)$ for some $g(x)$. So your basis has to be several polynomials which have a factor "$x-1$". Next, $\dim(P_2)=2+1=3$ but $W$ has the extra "$f(1)=0$" condition placed on it, so it would make sense to guess that $\dim(W)=2$. Thus look for $2$ polynomials with factor $x-1$ (one of degree 1 and one of degree 2). Good luck! :)
Apr
4
answered Proving that a set of polynomials P2 is a subspace of P3
Apr
4
revised Proving that a set of polynomials P2 is a subspace of P3
latex
Apr
1
revised How many methods are there for solving repeated roots of differential equations?
added 1 characters in body
Apr
1
answered How many methods are there for solving repeated roots of differential equations?
Apr
1
comment How many methods are there for solving repeated roots of differential equations?
Do you mean "...finding the solutions of a differential equation..."?