Finding Measuring Points in three-point perspective drawing
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Finding Measuring Points in three-point perspective drawing

In his Complete Guide to Perspective Drawing (page 39), Craig Attebery places Measuring Points of two-point perspective in a line perperdicular to that cr...

Published: Aug 10, 2026

Difference in the definitions of glb and lub in real analysis and abstract algebra
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Difference in the definitions of glb and lub in real analysis and abstract algebra

The following text is from the book Abstract Algebra by T. W. Judson : Let $X = {\{1,2,3,4,6,8,12,24}\}$ be the set of divisors of $24$ with the partial o...

Published: Aug 10, 2026

In a parallelogram, does the diagonal bisect the angles that they meet?
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In a parallelogram, does the diagonal bisect the angles that they meet?

I understand the following properties of the parallelogram: Opposite sides are parallel and equal in length. Opposite angles are equal. Adjacent angles ad...

Published: Aug 10, 2026

Two circles with a common external tangent problem. [closed]
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Two circles with a common external tangent problem. [closed]

Two circles are tangent externally at A, and a common external tangent touches them at B and C. The line segment BA is extended, meeting the second circle...

Published: Aug 10, 2026

Find normal vector of a 3d vector
general

Find normal vector of a 3d vector

I need to find the normal vector for the following 3d vector presented in the vectorial equation because I need to find a plane that is orthogonal to the ...

Published: Aug 10, 2026

Rank theorem on manifolds
updates

Rank theorem on manifolds

Rank theorem on manifolds says that : Suppose $M$ and $N$ are two smooth manifolds of dimensions $m$ and $n$, respectively, and $F:M\rightarrow N$ be a sm...

Published: Aug 10, 2026

Prove: $\operatorname{rank} A \leq 1$ iff $A=xy^T$ for some $x,y \in \mathbb{R}^{n \times 1}$. [duplicate]
updates

Prove: $\operatorname{rank} A \leq 1$ iff $A=xy^T$ for some $x,y \in \mathbb{R}^{n \times 1}$. [duplicate]

Let $A \in \mathbb{R}^{n \times n}$. Then $\operatorname{rank} A \leq 1$ if and only if $A = xy^T$ for some $x, y \in \mathbb{R}^{n \times 1}$. Need help....

Published: Aug 10, 2026

Is a function that is one-to-one necessarily onto?
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Is a function that is one-to-one necessarily onto?

I'd would like to know that, because I don't want to prove a function is onto if I don't have to. If the answer is no, is there any particu...

Published: Aug 10, 2026

Orientation(geometry) [closed]
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Orientation(geometry) [closed]

A xy-plane is rotated about x and y-axis. But when it is rotated along z-axis, it doesn't change the orientation of xy-plane, why? I've tried to...

Published: Aug 10, 2026

Complex variable limit at infinity
general

Complex variable limit at infinity

Is $\lim\limits_{z\to\infty} \frac{4z^2}{(z-1)^2}$, $z\in\mathbb{C}$, evaluated the same way as a real variable function limit? Or does one need to show s...

Published: Aug 10, 2026

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