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seen Jul 18 at 10:18

Dec
6
answered Prove by induction that $5^n - 1$ is divisible by $4$.
Dec
6
comment Prove by induction that $5^n - 1$ is divisible by $4$.
@user17762 $25 * 5 = 25 \mod 100$
Dec
2
revised What is the purpose of the first test in an inductive proof?
mathjax fixin
Dec
2
suggested suggested edit on What is the purpose of the first test in an inductive proof?
Nov
26
comment $ \theta $ is constructible if and only if $\sin \theta$ is constructible.
@CompuChip let me rephrase; constructing $\sin\theta$ make no sense without a unit length. If you want a length of $a \sin\theta$ then you can take $a$ as your unit length.
Nov
26
revised $ \theta $ is constructible if and only if $\sin \theta$ is constructible.
added 25 characters in body
Nov
26
comment $ \theta $ is constructible if and only if $\sin \theta$ is constructible.
@CompuChip you'll need some unit length in all cases anyway otherwise $sin\theta$ is meaningless
Nov
26
answered $ \theta $ is constructible if and only if $\sin \theta$ is constructible.
Nov
18
comment if matrix such $AA^T=A^2$ then $A$ is symmetric?
$AA^T=AA \Rightarrow A^{-1}AA^T=A^{-1}AA\Rightarrow A^T=A$
Nov
11
answered Measuring water puzzle
Nov
9
awarded  Student
Nov
9
revised How stable is my quaternion interpolation?
added 6 characters in body
Nov
8
asked How stable is my quaternion interpolation?
Nov
6
comment How can I determine that a relation lacks a property without using a counterexample?
you can try to find a contradiction with the assumption that the property holds for all, this proof by contradiction will also allow you to construct a counterexample
Oct
31
answered Exponential equation in x,y,z
Oct
26
comment What is the simplest proof of the pythagorean theorem you know?
@KeshavSrinivasan moreover it's easy to create a contraption like that in real life that proves $a^2+b^2$ is greater or less than $c^2$ by adjusting the depth
Oct
11
awarded  Yearling
Oct
3
comment Riddle: 1 question to know if the number is 1, 2 or 3
@Oleg567 what would you reply be if I gave you the command to say "no" if your number is 1, "don't know" if your number is 2, or "yes" if your number is 3?
Aug
29
comment Find the trace of the matrix?
the diagonal matrix with distinct numbers on the diagonal fits the description
Aug
27
answered Would the answer of the square root of a square root be positive or negative?