13,967 reputation
11936
bio website math.brown.edu/~lubinj
location Minnesota
age 78
visits member for 3 years
seen 6 hours ago

Aged mathematician


Oct
21
answered Can you cancel out a term if equal to zero?
Oct
20
comment how do I prove that $\mathbb{Q} [x]/\langle x^2 – 2 \rangle$ is a field
This is teh kind of answer I would have given.
Oct
20
answered Showing that $e^{-2} < \ln 2$
Oct
20
answered Algorithm to find the coefficient of GCD linear combination?
Oct
20
comment How does one find/list equivalence classes?
Well, that’s if you need to name them. Ordinarily, that’s not necessary.
Oct
19
comment How does one find/list equivalence classes?
I think if you count the number of classes (and I agree with your enumeration now), you’ll get a clue of how to describe them.
Oct
19
answered How does one find/list equivalence classes?
Oct
19
comment How does one find/list equivalence classes?
What do you mean by “find”? Do you mean just to describe them, or to count the number of things in each class, or what?
Oct
18
answered How to find the 4th degree polynomial with given values at $0,1,2,3,4$?
Oct
18
comment If $a\pmod 3 \equiv 1$ and $b\pmod 3 \equiv 2$, then $ab \pmod 3 \equiv 2$
To be pedantic, I point out that the original (and for mathematicians, right) way to write these relations is “$a\equiv b\pmod3$”. What’s going on is that $\equiv$ is a verb, and “modulo $3$” is an adverb modifying that verb. In Gauss’s Latin, “modulo $3$” means “with respect to the modulus $3$”.
Oct
18
comment line segment intersection strange results
Right. Here’s a case where it’s more reliable to write down the two equations (point-point formula, for instance, for each) and solve the pair of simultaneous equations that you get.
Oct
17
comment $\displaystyle\int \dfrac{\cos(x)+\sin(2x)}{\sin(x)}\text{ d}x$
Oh, sorry, I’m too old. I thought that the integral of tangent was well known, so cotangent (sort of) follows.
Oct
17
comment How do you solve this fraction?
“cross multiplication” is a technique that makes sense only when you have an equation, which you don’t.
Oct
17
comment $\displaystyle\int \dfrac{\cos(x)+\sin(2x)}{\sin(x)}\text{ d}x$
You don’t even need a substitution: after using the double-angle formula, separate the integrand into two fractions, each easily integrated.
Oct
17
answered line segment intersection strange results
Oct
16
awarded  Yearling
Oct
16
comment How can we show that it is an integer 5-adic number?
I prefer the completely simple-minded method I showed you in my answer to your other question, about $1/2$. It’s good for finding the quotient of any two $p$-adic numbers, not just integers.
Oct
16
comment What does the inequality stand?
This is a good example, but I wish you had written a few more words.
Oct
16
answered Power series in $\mathbb{Q}_5$
Oct
15
comment how find all the zeroes of the polynomial
In your try, you told no lies, but the form you got was not helpful to you, because you didn’t find the zeroes. You need a factorization that looks like $2x(x-r_1)(x-r_2)\dots$.