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1d
asked Could two different sums yield two different areas?
1d
accepted What's the necessary condition for that any three vectors are parallel to the edges of a triangle in the plane?
1d
accepted $1+2+3=\int_{0}^{\infty}t^3e^{-t} dt$?
1d
accepted Why the Ramsey number $R(2,4)$ is not equal to $2$?
2d
asked What's the importance of proving that $0,1$ are unique?
2d
comment Given the tetrahedron $OABC$, find a condition on $a OA+ b OB + c OC$ such that this is always inside $ABC$.
@corindo Thanks. But why is that condition true? I've been trying to prove it but have no success until now.
Sep
2
revised Given the tetrahedron $OABC$, find a condition on $a OA+ b OB + c OC$ such that this is always inside $ABC$.
added 22 characters in body
Sep
2
asked Given the tetrahedron $OABC$, find a condition on $a OA+ b OB + c OC$ such that this is always inside $ABC$.
Aug
31
comment What's the necessary condition for that any three vectors are parallel to the edges of a triangle in the plane?
What do you mean with $\overrightarrow{AB}\times\overrightarrow{AC}\neq0$? Inner product?
Aug
31
asked Write $CX,AY,BZ$ in terms of $CA,CB$ and the ratios $\alpha, \beta, \gamma$?
Aug
31
asked What's the necessary condition for that any three vectors are parallel to the edges of a triangle in the plane?
Aug
31
accepted Is non-paralellism transitive?
Aug
31
comment Is non-paralellism transitive?
Oh yes. Sorry, I'm stupid.
Aug
31
asked Is non-paralellism transitive?
Aug
30
comment What makes it legitimate to multiply both sides?
Yes, I know. But my question concerns to the formalization of this idea. See Berci's and anon's comments.
Aug
29
asked What makes it legitimate to multiply both sides?
Aug
29
comment Why the Ramsey number $R(2,4)$ is not equal to $2$?
Let me take an example. Taking all colorings of $K_2$, as it ahve only one edge, I'd have: $\{\{ edge1_{blue} \},\{ edge1_{red} \} \}$. I'd have both, no?
Aug
29
comment Why the Ramsey number $R(2,4)$ is not equal to $2$?
So, for all colorings, it must have a red $K_p$ or a blue $K_q$ or a red $K_q$ or a blue $K_p$?
Aug
29
asked Why the Ramsey number $R(2,4)$ is not equal to $2$?
Aug
29
reviewed Approve Gambler's Ruin With a Pay Schedule