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Trigonometrical Mnemonic

Published online by Cambridge University Press:  20 January 2009

John Alison
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If the functions be written as in the above figure, then

1. Of any three functions written consecutively on a circular arc or on a diameter, the mean is the product of the extremes. Thus sinA = tanAcosA, 1 = sinAcosecA, and so on.

2. In each triangle the square of the function written at the vertex turned downwards is equal to the sum of the squares of the functions written at the other two vertices. Thus I2 = sin2A + cos2A, and so on.

Type
Research Article
Information
Proceedings of the Edinburgh Mathematical Society , Volume 4 , February 1885 , pp. 88
Copyright
Copyright © Edinburgh Mathematical Society 1885