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1d
reviewed Approve Problem involving subspaces and linear transformations
2d
comment Why is The Following equality true? (limit of a sum and integrals)
en.wikipedia.org/wiki/Riemann_sum#/media/…
2d
comment What is the value of $k^2$
is $f`$ a typo or should it be $f'$ (with a single apostrophe)
2d
revised Prime number theory.
format, wording
Apr
28
comment Right Triangle's Proof
You write "Wikipedia" but you link to mathworld.wolfram.com/PythagoreanTriple.html . All in all it is a rather complicated and inelegant way to prove this simple fact.
Apr
28
revised How do I prove that $\lim_{z\to i} z^2=-1$?
format
Apr
28
comment A simple cubic equation problem:
And why can I suppose that $z_3=\dfrac{1}{\bar{z_1}}$?
Apr
28
comment Right Triangle's Proof
But if you check this three cases you get $b^2$ is $63$, $44$ or $23$. So 12 actually can't be the lenght of the hypotenuse because none of these numbers is a perfect square.
Apr
28
comment Right Triangle's Proof
No, I said if you want to check if 12 is the length of the hypotenuse $c$ you only have to check the three cases where $a$ is $9$, $10$ or $11$.
Apr
28
reviewed Edit Find derivative of $4\cos(x - \frac{311\pi}{180})$
Apr
28
revised Find derivative of $4\cos(x - \frac{311\pi}{180})$
fix \cdot instead of x and sin and cos
Apr
28
comment A simple cubic equation problem:
How does this imply that tthere is a root with absolute value 1?
Apr
28
revised Right Triangle's Proof
typos
Apr
28
revised Right Triangle's Proof
typo
Apr
28
answered Right Triangle's Proof
Apr
28
reviewed Approve Right Triangle's Proof
Apr
28
comment Solution of functional equation $f(x+y)=f(x)+f(y)+y\sqrt{f(x)}$
So there are four solutions.
Apr
28
comment Solution of functional equation $f(x+y)=f(x)+f(y)+y\sqrt{f(x)}$
$f(x) =0$ is a solution, too.And $f(x)=0$ if $x<0$ and $f(x)=\frac{x}{4}$ if $x \ge 0$ ...
Apr
25
comment Why can't a open interval in $\mathbb{R}$ be compact?
how are compactness and sequentially compactness related?
Apr
24
answered How to write the following polynomial in $(1-\frac{x}{a}) (1-\frac{x}{b}) (1-\frac{x}{c}) (1-\frac{x}{d})$?