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dbmag9
  • Member for 9 years, 2 months
  • Last seen more than a week ago
  • London, UK
7 votes
1 answer
81 views

Identifying a mathematical museum exhibit

5 votes
2 answers
129 views

Is there a graphical proof that $9n+1$ is triangular if $n$ is?

4 votes
2 answers
150 views

Do any compatible triangles make a tetrahedron?

4 votes
3 answers
145 views

Natural deduction proof that $(P\leftrightarrow \neg P)$ is a contradiction, without first deriving $(P\vee \neg P)$

3 votes
2 answers
169 views

Conventions on definitional if(f)

3 votes
3 answers
458 views

What proportion of triangles are acute?

2 votes
3 answers
45 views

What is wrong with my reasoning on this partitioning question?

1 vote
2 answers
62 views

Intuition for divergence of $\arctan \left(\frac{1}{\sqrt n}\right)$, the angle in the Spiral of Theodorus

1 vote
2 answers
266 views

Induction proof for sum $\sin(\theta)+\sin(3\theta)+\cdots$

0 votes
1 answer
84 views

Can a linear transformation have exactly one invariant line?

0 votes
1 answer
108 views

Finding perpendicular eigenvectors (secondary school level)