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visits member for 1 year, 6 months
seen Jul 20 at 10:22

Jul
2
comment Is $F(f)=\int_{a}^{b}\phi(f(t))dt$a differentiable function?
No problem, look at the updated answer ;-)
Jul
2
revised Is $F(f)=\int_{a}^{b}\phi(f(t))dt$a differentiable function?
added 1417 characters in body
Jul
2
comment Is $F(f)=\int_{a}^{b}\phi(f(t))dt$a differentiable function?
What you want to show is that there exists a linear $D_F \colon C(a,b)\to \mathbb R$ such that $$F(f+h)-F(f)= D_F(h) + \text o (h)\qquad h\to 0.$$
Jul
2
answered Is $F(f)=\int_{a}^{b}\phi(f(t))dt$a differentiable function?
Jul
2
awarded  Curious
Jun
21
answered What line does ω project vectors onto?
Jun
1
comment Find a non constant function that is a quotient of two polynomial, for which: $f\left(x+\frac{1}{f(x)}\right)=f(x)f(-x)$
How is that obvious to you?
May
8
comment If $n>1,$ and $I =\int^{\infty}_0 \frac{dx}{(x+\sqrt{1+x^2})^n}$ then find the value of I.
Do you know some complex analysis?
Feb
13
comment If $f,g$ are continuous at $a$, show that $h(x)=\max\{f(x),g(x)\}$ and $k(x)=\min\{f(x),g(x)\}$ are also continuous at $a$
You are welcome my friend :-)
Feb
13
answered If $f,g$ are continuous at $a$, show that $h(x)=\max\{f(x),g(x)\}$ and $k(x)=\min\{f(x),g(x)\}$ are also continuous at $a$
Feb
11
comment Question on conservative fields
@JesseMadnick if they are equivalent, why is it relevant?
Feb
10
answered directional derivatives implications
Feb
10
comment Limit of a solution of a Euler Lagrange differential equation
I thought the question was quiet interesting, let me know if I can improve it in some way, maybe provide more details about the context. Or would it be more suitable on Phys.SE ?
Feb
9
answered Conservation of Energy on Pendulum
Feb
9
asked Limit of a solution of a Euler Lagrange differential equation
Feb
3
comment Simple closed set proof
Well, I guess it really depends on (a) your taste (b) what kind of answer is requested in your assignment. What you are doing in your (correct) proof is essantially what is synthetized in lhf's answer or in mine, when I naively say that it's obvious that such sets are closed. The three ways are equivalent.
Feb
3
comment Simple closed set proof
You mean the “obviously close” statement? Well if it is for an exam, you'd better write something like “Suppose $x_1 <0$... if we take $\varepsilon >0$ very little, then... hence...” :-P
Feb
1
accepted Proof of $|\int _a ^b \mathbf f | \leq \int _a ^b |\mathbf f|$
Feb
1
accepted Definition of the Hamiltonian via Legendre transform.
Jan
30
answered Simple closed set proof