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NTS


Feb
21
comment Give an example of a sequence of smooth equicontinuous functions whose derivatives are unbounded
Have you tried the function I proposed?
Feb
21
comment Give an example of a sequence of smooth equicontinuous functions whose derivatives are unbounded
What about $f_n(x)=\dfrac{e^{nx}}{n}$?
Feb
21
comment Show that $d_b(x,y)=\frac{d(x,y)}{1+d(x,y)}$ is a metric.
You n.1 is wrong. you have $a/(1+a)$, and $a>0$, then $a/(1+a)<a$ because $a$ is less than $1+a$. Anyway, that point is as easy as: $a/(a+1)>0$ because $a>0$ because $a$ forms a metric space. Being $a=d(x,y)$
Feb
18
comment How to show that for $|x|<1$, $1+2x+3x^2+\cdots=\frac1{(1-x)^2}$?
thank you, I didn't know any of those.
Feb
17
comment How to show that for $|x|<1$, $1+2x+3x^2+\cdots=\frac1{(1-x)^2}$?
Can you please give me an example (link or whatever) in which when you have infinite terms the derivative is not the sum of derivatives?
Feb
17
answered Limit $(x,y)\to (0,0) (x^2 \cdot y^2)/(x^3 + y^3)$
Feb
16
answered Functions of algebra that deal with real number
Feb
16
comment A multiple choice question on determinant
@AndreasCaranti You're right.
Feb
16
answered A multiple choice question on determinant
Feb
15
answered How would you solve this differential equation: $\frac{d^2y}{dx^2} = \frac{100}{y}$?
Feb
14
comment Difference between imaginary and complex numbers
@HenningMakholm Mathematicians are professionals at finding these pathological examples... you're right :)
Feb
14
answered Difference between imaginary and complex numbers
Feb
14
answered Ethical problems in mathematics
Feb
14
answered Why don't Venn diagrams count as formal proofs?
Feb
14
comment Finding inverse of a $3\times3$ matrix
Well, for 3x3 matrices, and by hand, I do it a lot faster b the adjungated matrix than by the elementary operations.
Feb
14
revised What is a vector?
edited tags
Feb
14
comment A question around concept of derivative
I am, but some parragraph separation would be appreciated. That's why it's hard, not because it's explaines. Also so many inline equations are not great either. Main equations should be centered in their own line. You won't find math books written like that.
Feb
14
comment A question around concept of derivative
My God, that's hard to read.
Feb
14
comment Cubical delusion : Cubes one coloured red and other green except on 1 face are cut into 27 & 64 cubes. How many are red only on 1 face?
I think that from your interpretations, your answers are right. I would say 22. I don't get why the problem says: "which are mixed up with other cubes." ¿Why is that relevant?
Feb
14
comment Finding inverse of a $3\times3$ matrix
@CBenni I think it does work for abritrarily big matrices... According to wikipedia, it does.