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Isomorphism
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24 votes
1 answer
826 views

To prove that $2^{3n}+2^n +1$ is not a perfect square.

16 votes
4 answers
14k views

How do we check if a polynomial is a perfect square?

14 votes
0 answers
522 views

The right way to motivate lattice theory in a combinatorics class

12 votes
1 answer
598 views

On the impossibility of proving certain problems using double counting.

11 votes
1 answer
264 views

Are there infinitely many pairs of primes where each divides one more than the square of the other?

10 votes
3 answers
191 views

A trigonometric integral (guessed from a combinatorics formula)

9 votes
1 answer
897 views

How does one show that multiples of number does not have a zero in the decimal expansion?

8 votes
1 answer
846 views

Explicit computation of a 3-form on SU(2)

8 votes
2 answers
23k views

The equation of a pair of tangents to a circle from a point.

6 votes
1 answer
119 views

Conditions on solutions of a diophantine equation.

6 votes
0 answers
1k views

Elementary proof of Monsky's theorem

6 votes
2 answers
203 views

Looking for a source of an infinite trigonometric summation and other such examples.

6 votes
1 answer
776 views

A Inequality between Bhattacharyya distance and KL divergence

6 votes
0 answers
312 views

Is there a Mazur–Ulam theorem equivalent for vector spaces over finite fields?

6 votes
1 answer
106 views

Summing a series with binomial coefficients without calculus.

5 votes
1 answer
534 views

Is $2^\infty$ uncountable and is cardinality a continuous function?

5 votes
2 answers
1k views

Minimal dense subset of $\mathbb{Q} \cap [0,1]$

5 votes
1 answer
2k views

Generating the special linear group of 2 by 2 matrices over the integers.

5 votes
1 answer
86 views

Are there more examples of functional equations which are also valid for the identity map?

5 votes
0 answers
93 views

A nice formula for area of the triangle [duplicate]

5 votes
1 answer
3k views

The trick to proving trigonometric identities

5 votes
1 answer
144 views

On the notion of arrows in a category of pro-objects

4 votes
5 answers
762 views

Find an angle in the given quadrilateral

4 votes
0 answers
67 views

Arnold's combinatorial description of entropy.

4 votes
1 answer
3k views

The properties of graph and its relation with the largest eigenvalue

4 votes
2 answers
946 views

Maximal commutative subring of the ring of $2 \times 2$ matrices over the reals

4 votes
2 answers
337 views

Insight of some concepts in commutative algebra

4 votes
2 answers
3k views

Puzzle: Guessing the bigger number!

4 votes
1 answer
3k views

Teaching probability by using a deck of cards

4 votes
0 answers
48 views

References for doing geometry using "higher degree curves as fundamental objects."