Question

Locus of centres of circles tangent to two fixed circles?

score 694 · Answer 1 · 2026-04-12 16:07:31

694

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Locus of centres of circles tangent to two fixed circles?

Published on 12 Apr 2026 - 16:07

score 1.3k · Answer 2 · 2026-03-27 16:55:19

1.3k

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Image of a circle under conformal map $1/z$

Published on 27 Mar 2026 - 16:55

score 1.3k · Answer 3 · 2015-12-08 06:55:08

1.3k

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What is the spherical law of cosines in high dimensions?

Published on 08 Dec 2015 - 6:55

score 100 · Answer 4 · 2026-03-29 02:46:51

100

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Show that if $\angle ADB = 60^{\circ}$ then $AA_1 = BB_1$ (and answer whether the converse is true).

Published on 29 Mar 2026 - 2:46

score 1.4k · Answer 5 · 2015-12-09 19:10:00

1.4k

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How to find the point of intersection

Published on 09 Dec 2015 - 19:10

score 3k · Answer 6 · 2015-12-10 07:27:44

3k

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Must perpendicular (resp. orthogonal) lines meet?

Published on 10 Dec 2015 - 7:27

score 94 · Answer 7 · 2015-12-10 14:18:36

94

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Find BC/AB if I lies in the circumcircle of AEF

Published on 10 Dec 2015 - 14:18

score 102 · Answer 8 · 2015-12-10 14:29:49

102

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Proving that the midponts of an isosceles trapezoid are collinear

Published on 10 Dec 2015 - 14:29

score 182 · Answer 9 · 2015-12-10 20:40:47

182

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Show that the only point in the interior of triangle ABC that is its own isogonal conjugate is the incenter.

Published on 10 Dec 2015 - 20:40

score 121 · Answer 10 · 2015-12-10 23:12:20

121

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If the Lemoine point of triangle ABC lies on the altitude from vertex C, show that either AC = BC or angle C =90 degrees.

Published on 10 Dec 2015 - 23:12

score 258 · Answer 11 · 2026-04-24 00:00:14

258

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Is this a valid proof that the sum of the angles in a triangle is $180^\circ$?

Published on 24 Apr 2026 - 0:00

score 1.9k · Answer 12 · 2026-04-18 18:18:14

1.9k

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What is the length of [BC]?

Published on 18 Apr 2026 - 18:18

score 379 · Answer 13 · 2026-03-28 04:40:58

379

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What is exactly a “Point”?

Published on 28 Mar 2026 - 4:40

score 66 · Answer 14 · 2026-03-29 14:01:47

66

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Matrices representing symmetries

Published on 29 Mar 2026 - 14:01

score 226 · Answer 15 · 2026-04-09 07:32:21

226

Views

Jigsaw-style proofs of the Pythagorean theorem with non-square squares

Published on 09 Apr 2026 - 7:32

List Question

Locus of centres of circles tangent to two fixed circles?

Image of a circle under conformal map $1/z$

What is the spherical law of cosines in high dimensions?

Show that if $\angle ADB = 60^{\circ}$ then $AA_1 = BB_1$ (and answer whether the converse is true).

How to find the point of intersection

Must perpendicular (resp. orthogonal) lines meet?

Find BC/AB if I lies in the circumcircle of AEF

Proving that the midponts of an isosceles trapezoid are collinear

Show that the only point in the interior of triangle ABC that is its own isogonal conjugate is the incenter.

If the Lemoine point of triangle ABC lies on the altitude from vertex C, show that either AC = BC or angle C =90 degrees.

Is this a valid proof that the sum of the angles in a triangle is $180^\circ$?

What is the length of [BC]?

What is exactly a “Point”?

Matrices representing symmetries

Jigsaw-style proofs of the Pythagorean theorem with non-square squares

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