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**Pythagorean**

This applies to rules with a P scale.

To find the value of Ö(1-x^{2}):

- Move the cursor to the x value on the D scale.
- Read the value of Ö(1-x
^{2}) on the P scale.

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

For right angled triangles, c^{2} = b^{2} - a^{2}

then

c = b Ö(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 Ö(1-s^{2})
and highlighted in green.)

10 on C to cursor,

Answer (4.0) under 5.0 on D.

For cosine the formula is:

cos = Ö(1- sin^{2})

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