Question

Given $\cos^2 x = 2 \sin x \cos x$, why can't I cancel $\cos x$ to get $\cos x = 2 \sin x$?

score 630 · Answer 1 · 2018-09-07 00:52:18

630

Views

Given $\cos^2 x = 2 \sin x \cos x$, why can't I cancel $\cos x$ to get $\cos x = 2 \sin x$?

Published on 07 Sep 2018 - 0:52

score 264 · Answer 2 · 2018-09-07 05:54:16

264

Views

Solve for $\theta$: $x = \theta - \sin\theta$

Published on 07 Sep 2018 - 5:54

score 1.3k · Answer 3 · 2018-09-07 08:21:53

1.3k

Views

Volume of a tetrahedron whose 4 faces are congruent.

Published on 07 Sep 2018 - 8:21

score 35 · Answer 4 · 2026-03-25 21:01:17

35

Views

rotated straight line substending an angle at the x-y axis

Published on 25 Mar 2026 - 21:01

score 136 · Answer 5 · 2026-03-16 13:46:25

136

Views

Is there an equivalent to trigonometry for solid angles?

Published on 16 Mar 2026 - 13:46

score 2.3k · Answer 6 · 2018-09-07 17:50:30

2.3k

Views

Express arccos in terms of arctan

Published on 07 Sep 2018 - 17:50

score 95 · Answer 7 · 2026-03-25 02:59:32

95

Views

Proving rules for real numbers hold for complex numbers

Published on 25 Mar 2026 - 2:59

score 60 · Answer 8 · 2026-03-25 20:12:00

60

Views

Find the roots (real or complex) of the equation $2a^2(1+\cos x) - (1+a^2 +b^2)^2 = 0$, $a,b\in \mathbb{R}$.

Published on 25 Mar 2026 - 20:12

score 50 · Answer 9 · 2018-09-08 12:50:46

Express $x$ in terms of $a$ and $b$: $\sin^{-1} {\frac{2a}{1+a^2}} + \sin^{-1}{\frac{2b}{1+b^2}} = 2\tan^{-1}x$

score 47 · Answer 10 · 2018-09-08 14:01:41

47

Views

Solving a differential equation with trigonometric functions

Published on 08 Sep 2018 - 14:01

score 956 · Answer 11 · 2026-04-01 09:54:06

956

Views

How to write $4-3i$ in the form $e^z$ with $z=x+yi$

Published on 01 Apr 2026 - 9:54

score 74 · Answer 12 · 2018-09-08 23:10:20

74

Views

Given real angles $\phi_1,\ldots,\phi_N$, there exist infinitely many integers $n$ such that $\cos(n\phi_k) > 0$ for all $k$.

Published on 08 Sep 2018 - 23:10

score 271 · Answer 13 · 2018-09-09 00:54:56

271

Views

How to prove that $\sin(\sqrt{x})$ is not periodic?

Published on 09 Sep 2018 - 0:54

score 86 · Answer 14 · 2026-03-26 04:32:08

86

Views

Aperiodicity of $\sin[2x+\cos(\sqrt{2}x)]$

Published on 26 Mar 2026 - 4:32

score 183 · Answer 15 · 2026-03-26 00:53:32

183

Views

Period of curve defined by trig functions (on a torus)

Published on 26 Mar 2026 - 0:53

List Question

Given $\cos^2 x = 2 \sin x \cos x$, why can't I cancel $\cos x$ to get $\cos x = 2 \sin x$?

Solve for $\theta$: $x = \theta - \sin\theta$

Volume of a tetrahedron whose 4 faces are congruent.

rotated straight line substending an angle at the x-y axis

Is there an equivalent to trigonometry for solid angles?

Express arccos in terms of arctan

Proving rules for real numbers hold for complex numbers

Find the roots (real or complex) of the equation $2a^2(1+\cos x) - (1+a^2 +b^2)^2 = 0$, $a,b\in \mathbb{R}$.

Express $x$ in terms of $a$ and $b$: $\sin^{-1} {\frac{2a}{1+a^2}} + \sin^{-1}{\frac{2b}{1+b^2}} = 2\tan^{-1}x$

Solving a differential equation with trigonometric functions

How to write $4-3i$ in the form $e^z$ with $z=x+yi$

Given real angles $\phi_1,\ldots,\phi_N$, there exist infinitely many integers $n$ such that $\cos(n\phi_k) > 0$ for all $k$.

How to prove that $\sin(\sqrt{x})$ is not periodic?

Aperiodicity of $\sin[2x+\cos(\sqrt{2}x)]$

Period of curve defined by trig functions (on a torus)

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