The purpose of this thread is to provide a link to posts that have geometric proofs. I shall gradually add to the list. From time to time I may move items about in the list to make it easier to find a particular item.

If you have requests, please reply in this thread and I’ll try to find (or create) what you want. Use the usual Help Me section if you need help with a particular problem. Normally I wouldn’t delete someone’s post, but I reserve the right to do so in this thread if it is becoming hard to keep track of new requests.

Two tangents to a circle from the same point are equal.

http://www.mathisfunforum.com/viewtopic … 09#p365709

post 6

Angle properties of a circle.

http://www.mathisfunforum.com/viewtopic.php?id=17799

Posts 6 and 7

The circumcircle

http://www.mathisfunforum.com/viewtopic.php?id=22507

The orthocentre

http://www.mathisfunforum.com/viewtopic.php?id=22510

The Inscribed Circle

http://www.mathisfunforum.com/viewtopic … 21#p368021

Nine point circle

http://www.mathisfunforum.com/viewtopic.php?id=22509

The Sine Rule

http://www.mathisfunforum.com/viewtopic.php?id=22508

Intersecting chords theorem

If A, B, C and D are points on a circle , P is a point inside the circle where AB and CD intersect, then AP.BP = CP.DP.

If AB and CD intersect externally, the theorem still holds.

http://www.mathisfunforum.com/viewtopic … 92#p368592

Isometries

If two 2D shapes are congruent then the transformation that maps one onto the other is called an isometry.

http://www.mathisfunforum.com/viewtopic … 18#p372518

tan(36)

http://www.mathisfunforum.com/viewtopic … 87#p378587

The Regular Icosahedron

http://www.mathisfunforum.com/viewtopic.php?id=22966

Bob

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