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There's a typo while calculating ||r'(t)||, that is the magnitude of the tangent vector. You have written,

(1)It should be $\sqrt{R^2} = R$

obviously.

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sudoankit 12 Dec 2017 12:20

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in discussion Hidden / Per page discussions » Submitting an Error on Math Online

There's a typo while calculating ||r'(t)||, that is the magnitude of the tangent vector. You have written,

(1)\begin{align} \| \vec{r'}(t) \| = \sqrt{R^2 \sin ^2 t + R^2 \cos ^2 t} = \sqrt{R^2} = R^2 \end{align}

It should be $\sqrt{R^2} = R$

obviously.

About the Theorem 2 on the page "the-curvature-of-straight-lines-and-circles" by sudoankit, 12 Dec 2017 12:20

Meh (guest) 05 Dec 2017 14:52

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in discussion Hidden / Per page discussions » Submitting an Error on Math Online

On the tietze-transformations page, in the example, the last line deletes the variable a, which changes the group. Instead I think the variable z should have been added first, with z=a.

Chaaben (guest) 29 Nov 2017 14:37

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in discussion Hidden / Per page discussions » Submitting an Error on Math Online

Hi,

on the page: Properties of Adjoints of Linear Maps

Proposition 3: Proof: We note that <(T*)*(v),w> = <v,(T*)*(w)>

I think it should be: <(T*)(v),w> = <v,(T*)*(w)>

Thank you

Hi,

on the page: Eigenvalues and Eigenvectors Examples 1

In the Example 3, the converse direction of the proof: … Since[[ T^{-1}$ is also …

Thank you

Chaaben (guest) 27 Nov 2017 19:12

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in discussion Hidden / Per page discussions » Submitting an Error on Math Online

Hi,

on the page: Linear Maps

An equivalent definition … T(u+v) + T(u) + T(v) (Additivity)

I think it should be, T(u+v) = T(u) + T(v) (Additivity)

Thank you

Chaaben (guest) 27 Nov 2017 15:45

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in discussion Hidden / Per page discussions » Submitting an Error on Math Online

Hi,

on the page: Range of a Linear Map

Proof of Lemma 2, the fifth point: From Lemma 1, we have that 0W = range(T).

I think it should be, 0W ∈ range(T).

Thank you

Chaaben (guest) 27 Nov 2017 14:01

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in discussion Hidden / Per page discussions » Submitting an Error on Math Online

Hi,

on the page: Eigenvalues and Eigenvectors Examples 3

In Example 1: 3y = λ(λy

2)

I think it should be 3y = λ(λy)/2

Thank you

Chaaben (guest) 26 Nov 2017 10:31

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in discussion Hidden / Per page discussions » Submitting an Error on Math Online

Hi,

on the page: Injective, Surjective, and Bijective Functions

At the bottom of the page: In the examples from earlier, we see that f is both injective and surjective, so g is bijective.

I think it should be, f is bijective.

Thank you

Chaaben (guest) 25 Nov 2017 13:35

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in discussion Hidden / Per page discussions » Submitting an Error on Math Online

Hi,

on the page: Self-Adjoint Linear Operators

The example T(x,y)=(2x+3y,3x+2y): Note that T(1,0)=(2,3) and T(0,1)=(3,0).

So T(0,1) should be equal to (3,2).

Thank you

Chaaben (guest) 25 Nov 2017 12:30

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in discussion Hidden / Per page discussions » Submitting an Error on Math Online

Hi,

on the page: Polynomials Applied to Linear Operators Examples 2

At the bottom of the page: We have that then every zero, λ1,λ2,…,λm is an eigenvalue of T.

I think it is meant, every nonzero λ1,λ2,…,λm

Thank you

Chaaben (guest) 25 Nov 2017 11:11

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in discussion Hidden / Per page discussions » Submitting an Error on Math Online

Hi,

on the page: The Ring of Polynomials with Ring Coefficients

The sixth requirement: For all a, b ∈ R we have that a∗b=b∗a (Closure under ∗).

I think it should be: For all a, b ∈ R we have that a∗b ∈ R

Thank you

Sectra (guest) 24 Nov 2017 11:23

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in discussion Hidden / Per page discussions » Submitting an Error on Math Online

In the "The Law of Syllogism" I think it should be: ((p->q) and (q->r)) -> (p->r)

Hi,

on the Page: The Baire Category Theorem Review

On The Baire Category Theorem for Complete Metric Spaces page we … open and ##gold|dense#3 sets in X.

It is about the symbol # and the word gold.

Thank you

Krait (guest) 30 Oct 2017 17:49

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in discussion Hidden / Per page discussions » Submitting an Error on Math Online

The Characterization Theorem for Intervals

I just discovered this web and it's awesome, thank you so much! I was reading the Characterization Theorem and two things sound weird to me:

-In Case 2, I believe there is a bracket missing in the 4th line: z\in[x,y

-In Case 3, I believe that inf(S) proves that S subset [a,infinity), not (a,infinity).

heliostat9 28 Oct 2017 01:10

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in discussion Hidden / Per page discussions » Submitting an Error on Math Online

Equation (6) and preceding line: replace ' dx/dz|y i.e. partial of x with respect to z at constant y ' with

' dy/dz|w i.e. partial of y with respect to z at constant w '.

KaTuripu 27 Oct 2017 15:06

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in discussion Hidden / Per page discussions » Submitting an Error on Math Online

here is the mistake :

"Note that the definitions of an algebra and a σ-algebra on a set X are similar. The only difference is that an **algebra** on a set X is closed under finite unions, while an **algebra** on a set X is closed under countably infinite unions.//"

Hi,

Thank you for your website. I have found these typos in the page "

Bases of a Topology"

In the line after Eq. 2, it should be written as,

U is subset of P(X).

In the last line of the page, it should be written as,

Therefore every….

Thank you.

MTT

Chaaben (guest) 07 Oct 2017 16:21

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in discussion Hidden / Per page discussions » Submitting an Error on Math Online

Hi,

the name of the page: Bounded Sequences of Real Numbers.

Conversely, if |an| ≤ M0 for every n ∈ N then M0 ≤ an ≤ M0 for all n ∈ N.

I think it should be: Conversely, if |an| ≤ M0 for every n ∈ N then -M0 ≤ an ≤ M0 for all n ∈ N.

The minus sign before M0 is missing.

Thank you very much.

Aaron (guest) 07 Sep 2017 05:50

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in discussion Hidden / Per page discussions » Submitting an Error on Math Online

In your page "Derivative Notation", you mentioned that one limitation in "Euler's Notation" is that it is unable to express what variable differentiation is done with respect to. However, at least according to "The Differential and Integral Calculus" (1842) by Augustus De Morgan (pp. 268; a preview can be found on Google Books) the notation is modified using a subscript of the variable when it is ambiguous. This could be edited so as not to contain an unfair portrayal of the notation.

Nachoo (guest) 28 Jul 2017 09:18

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in discussion Hidden / Per page discussions » Submitting an Error on Math Online

Calculus - Continuity of a function - Example one:

Shouldn't it be x²+2/x if x > -2 instead of x²-2/x

Best regards and thx for making this awesome website!

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