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Proving Odom's Golden Ratio Construction

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Edited by Richard Walker, Saturday 6 June 2026 at 00:49

This follows on from my last post.

It is a well-known result that in any triangle the centroid divides each median in the ratio 2:1. The length of CG is 1 because it a radius of the circumcircle and so we have GE = one divided by two and CE = one plus one divided by two equals three divided by two .

Because U and V are midpoints F must be the midpoint of CE, so CF = one divided by two multiplication three divided by two equals three divided by four and FG = one minus three divided by four equals one divided by four .

Note also that from the fact that V is the midpoint of BC and the symmetry of the equilateral triangle we have GV = GE = one divided by two .

Now we can apply Pythagoras' Theorem, first in triangle GFV and then in GFW, to find lengths FV and FW.

In GFV, FV2 = GV2 - GF2 = left parenthesis one divided by two right parenthesis squared minus left parenthesis one divided by four right parenthesis squared equals three divided by 16 . So FV = Square root of three divided by four .

In GFW, FW2 = GW2 - GF2 = 1 - left parenthesis one divided by four right parenthesis squared = 15 divided by 16 . So FW = Square root of 15 divided by four = Square root of three times Square root of five divided by four .

Finally, UV = 2 x FV = Square root of three divided by two ; UW = UV + FW = Square root of three divided by four + Square root of three times Square root of five divided by four ; and so cap u times cap w divided by cap u times cap v = ( Square root of three divided by four + Square root of three times Square root of five divided by four ) ÷ ( Square root of three divided by two ) = one plus Square root of five divided by two = phi , as claimed.

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