Date: Sun 1/31/99 9:20 AM
From: Alex Bogomolny
45° is obviously trisectable because it is constructible as is 60°. Then 15° = 60° - 45° is also constructible.
15° is not trisectable because if it were, so would be 60° which we know is not.
All the best,
Alexander Bogomolny
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