Discovered and proved in 1898 by the British mathematician Frank Morley (1860–1937), who became a university professor in the United States, the theorem that bears its discoverer's name and made him famous looks innocuous enough:
The intersection points of adjacent trisectors of the angles of any triangle ABC are the vertices of an equilateral triangle DEF.
An equilateral triangle can thus spring from any triangle: that is the surprising feature of this result, which has been proved many times by various geometric and trigonometric methods, yet still retains its sense of wonder.
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