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Ziqi Fan
  • Member for 1 year, 7 months
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4 votes

Does "Let" imply existence?

4 votes

Finding the angle between $x-5=0$ and $2x+2y-7=0$

3 votes
Accepted

When we write $y'' + y' + y = x$, for a function $y$, do we really mean $y''(x) + y'(x) + y(x) = x$?

3 votes

$y=\sin^2x+\sin x+1$. Find the range of $y$

2 votes

Confusion about limits, specifically the definition of a limit

2 votes

Formal Definition of Summation over a Set

2 votes
Accepted

Counterexamples for $\alpha < \beta \Longrightarrow \alpha^{\gamma} < \beta^{\gamma}$, where $\alpha$, $\beta$ and $\gamma$ are nonzero ordinals

1 vote
Accepted

Seeking Proof for a Conclusion from Positive Definite Homogeneous Polynomials

1 vote

Derivative of a function at a constant point

1 vote

What's the best way for an engineer to learn "real" math?

1 vote

Confusion on notation of multivariable differentiation in n-dimensional space for matrices (gradients)

1 vote

If $f$ is a real function, continuous at $a$ and $f(a) < M$, then there is an open interval $I$ containing a such that $f(x) < M$ for all $x \in I$.

1 vote

Limit of a function with an undefined feature

0 votes

Help with truth statements "For all $x \in \varnothing, p(x)$" and "$\exists x \in \varnothing, p(x)$ "

0 votes
Accepted

Why $y^2\ge x^4$ can be written as $|y|\ge x^2$?

0 votes

Why do proof authors use natural language sentences to write proofs?

0 votes

Well ordering principle for rationals

0 votes

What is the meaning of "$\pm$"? Can we write $1=\pm1$? or $x^2=4\iff \pm x=\pm 2$?

0 votes
Accepted

Evaluate $\exp\bigg(-\dfrac{x^2}{2} + 4x \bigg) \text{ as } x \to \infty.$