Question

Prove $\sin x + \sin 3x + \cdots + \sin(2n-1)x = \frac{\sin^2 nx}{\sin x}$ is true

score 95 · Answer 1 · 2026-04-16 10:00:00

95

Views

Prove $\sin x + \sin 3x + \cdots + \sin(2n-1)x = \frac{\sin^2 nx}{\sin x}$ is true

Published on 16 Apr 2026 - 10:00

score 77 · Answer 2 · 2026-04-13 16:04:18

77

Views

Proving a tricky set of inequalities with double induction

Published on 13 Apr 2026 - 16:04

score 153 · Answer 3 · 2026-04-15 21:13:24

153

Views

can you perform induction by assuming k and k+1 and showing difference is correct.

Published on 15 Apr 2026 - 21:13

score 152 · Answer 4 · 2026-04-16 05:27:35

152

Views

Sum expansion of the elementary symmetric polynomials

Published on 16 Apr 2026 - 5:27

score 44 · Answer 5 · 2026-04-13 07:32:22

44

Views

Help save proof about existence of open sets $x \in U$, $K \subset V \subset Y: \| f(u,v) - f(x,v)\| < r$, where $f: U \times V \to E$, $K$ compact

Published on 13 Apr 2026 - 7:32

score 69 · Answer 6 · 2026-04-17 14:31:38

69

Views

Proof by Cases [discrete mathematics]

Published on 17 Apr 2026 - 14:31

score 66 · Answer 7 · 2026-04-10 11:33:29

66

Views

Direct proof of Universal Set [discrete mathematics]

Published on 10 Apr 2026 - 11:33

score 303 · Answer 8 · 2026-04-14 22:14:06

303

Views

Draw a pentagon with any 2 angle sums being less than $216^o$

Published on 14 Apr 2026 - 22:14

score 66 · Answer 9 · 2026-04-11 11:09:28

66

Views

Big-$O$ verification [discrete mathematics]

Published on 11 Apr 2026 - 11:09

score 85 · Answer 10 · 2026-04-09 13:51:59

85

Views

Universal set proof [discrete mathematics]

Published on 09 Apr 2026 - 13:51

score 70 · Answer 11 · 2026-04-16 04:56:23

70

Views

Q: Prove that for any natural number, there exists a multiple that (in decimal form) only uses digits 0 and 1

Published on 16 Apr 2026 - 4:56

score 316 · Answer 12 · 2026-04-15 19:07:29

316

Views

Proving $\forall x \in \Bbb R$ and $ \epsilon \gt 0$, $N(x;\epsilon) \backslash \{x\}$ is open.

Published on 15 Apr 2026 - 19:07

score 40 · Answer 13 · 2026-04-16 11:54:05

40

Views

If $X$ is a set of ordinals then so is $\bigcup X$

Published on 16 Apr 2026 - 11:54

score 623 · Answer 14 · 2026-04-15 20:56:51

623

Views

Equivalent norms and subsets of open balls PROOF

Published on 15 Apr 2026 - 20:56

score 62 · Answer 15 · 2026-04-16 05:34:05

62

Views

In showing that if $V=X \oplus Y$, then $X \cap Y = \{0\}$, is writing $v=0+v$ and $v=v+0$ for $v \in X \cap Y$ sufficient?

Published on 16 Apr 2026 - 5:34

List Question

Prove $\sin x + \sin 3x + \cdots + \sin(2n-1)x = \frac{\sin^2 nx}{\sin x}$ is true

Proving a tricky set of inequalities with double induction

can you perform induction by assuming k and k+1 and showing difference is correct.

Sum expansion of the elementary symmetric polynomials

Help save proof about existence of open sets $x \in U$, $K \subset V \subset Y: \| f(u,v) - f(x,v)\| < r$, where $f: U \times V \to E$, $K$ compact

Proof by Cases [discrete mathematics]

Direct proof of Universal Set [discrete mathematics]

Draw a pentagon with any 2 angle sums being less than $216^o$

Big-$O$ verification [discrete mathematics]

Universal set proof [discrete mathematics]

Q: Prove that for any natural number, there exists a multiple that (in decimal form) only uses digits 0 and 1

Proving $\forall x \in \Bbb R$ and $ \epsilon \gt 0$, $N(x;\epsilon) \backslash \{x\}$ is open.

If $X$ is a set of ordinals then so is $\bigcup X$

Equivalent norms and subsets of open balls PROOF

In showing that if $V=X \oplus Y$, then $X \cap Y = \{0\}$, is writing $v=0+v$ and $v=v+0$ for $v \in X \cap Y$ sufficient?

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