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graydad

A retired mathematician that has become a software developer. I still have a soft spot for mathematics.

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34
What's wrong with l'Hopital's rule?
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29
What is an example of function $f: \Bbb{N} \to \Bbb{Z}$ that is a bijection?
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20
Why/How does this sqrt term work? The inverse of a fraction in a sqrt
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17
Easy math proofs or visual examples to make high school students enthusiastic about math
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13
Proof: The identity matrix is invertible and the inverse of the identity is the identity
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12
Chain rule with triple composition
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12
How do I determine if a set is open or closed??
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11
What to answer when people ask what I do in mathematics
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11
Doubt about the domain in logarithmic functions.
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11
The coefficient of $x^9$ in the expansion of $(1+x)(1+x^2)(1+x^3)\cdots(1+x^{100})?$
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10
Why is the cube-root of $x$ 'odd'?
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10
Why is $-5^2=-25$?
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9
subtracting inequalities if difference is positive
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8
If $e^{i\theta}=e^{i\varphi}$, then $\theta-\varphi=2k\pi$
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8
Integrate $ \int \frac{x^2}{x+1} dx $
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8
Roots of a cubic
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7
How to solve $z^6+i=0$
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7
If $a$ and $b$ are positive real numbers, then $a + b \geq 2 \sqrt{ab}$.
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7
Find the number of positive integers solutions of the equation $3x+2y=37$
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7
Even and odd proof - if n is even then $n^{2} -1$ is odd.
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6
Solve the equation $4^{7 x - 10} = 10^{7 x - 6}$ for $x$
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6
Why is this limit $\lim_{n \to \infty}(1 + \frac{1}{n})^n$ equal to $e$?
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6
How to prove $\sqrt\frac{1 - \sin x}{1 + \sin x} = \frac{1}{\cos x} - \tan x$
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6
Prove A is an open set if and only if $A \cap Bd(A) = \emptyset $
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6
When I prove two topologies are same, is it sufficient to prove they have same basis? If so,Why?
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6
why $ \sum_{k=0}^{\infty} x^{2k} = \frac{1}{1-x^2}\\$
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6
Find an increasing sequence of rationals that converges to $\pi$
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5
Inequality with prime numbers
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5
About the divergence of $\sum^\infty_{n=1}\frac 1 {n\cdot n^{1/n}}$
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5
Does this series $\sum_{i=0}^n \frac{4}{3^n}$ diverge or converge?
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