Slide rules HOME page INSTRUCTIONS A-to-Z

Pythagorean

This applies to rules with a P scale.

To find the value of (1-x2):

This scale can be used either for right angled triangles or for converting sin to cos (and vice versa).

For right angled triangles, c2 = b2 - a2
rt-angle.gif (1031 bytes)
then
c = b (1- (a/b)2 )

Example:
    b=5.0 and a = 3.0 How long is c
    Calculate a/b = 3.0/5.0 = 0.6
    Cursor to 0.6 of Pythagorean scale (marked (1-s2) and highlighted in green.)
    10 on C to cursor,
    Answer (4.0) under 5.0 on D.

pythag.jpg (26060 bytes)

For cosine the formula is:

cos = (1- sin2)

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