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| Not So Simple Sines (Posted on 2009-12-24) |
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Analytically prove sin(54)-sin(18) = 1/2
Is this analytical?
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 | Comment 3 of 4 | 
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Not exactly analytical – but I can’t resist...
Imagine a regular pentagon ABCDE with unit sides.
Let M be the mid-point of AB.
Let DM cross CE at G (they’re perpendicular).
Let F be the foot of the perpendicular from A to CE.
Then: Angle EDG = 54 deg and Angle EAF = 18 deg.
EG – EF = FG = AM therefore sin 54 – sin 18 = 1/2
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Posted by Harry
on 2010-01-11 14:57:18 |
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