Maybe one way is that if you have sinx=y , where y is a number, find from the tables for which x you have y.

Then if you find x, find x/2 and from the tables again find sin(x/2)

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- July 24th 2009, 03:19 AM #1

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- July 24th 2009, 03:36 AM #2

- July 24th 2009, 03:38 AM #3

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- July 24th 2009, 03:42 AM #4

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- July 24th 2009, 03:47 AM #5

- July 24th 2009, 03:48 AM #6

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- July 24th 2009, 03:59 AM #7

- July 24th 2009, 04:00 AM #8
Is there 22.5 in a trig table ? -_-

Note that since 45 is in the first quadrant, 45/2 is also in the first quadrant.

We know that

So

Let

Then

This is a quadratic equation. In your situation, we have :

Solve for T, by remembering it's positive (because it's a square)

And then take its square root, by remembering that it must be positive (because x/2 is in the first quadrant)

- July 24th 2009, 04:00 AM #9

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