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I've been slaving over this for a couple days now and I can't seem to get a resolution at all.
Can anyone solve for $\alpha$? example

Given data is the length of the red line that isn't tangential, $\angle$ $\delta$, $\angle$L and The length of the radius of the circle.

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    What is the data given on this problem ?2012-09-27
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    The given data is $\partial$ and L. I probably shouldn't have used $\partial$ as a variable :S2012-09-27
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    So, the radius of the circle is not given?2012-09-27
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    I misspoke, Radius of the circle is given aswell, I've edited my question.2012-09-27

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Since you have the lengths and directions of two sides of the triangle, you can compute the coordinates of its right-hand vertex relative to the centre of the circle; their ratio gives you $\tan\alpha$:

$$ \alpha=\arctan\frac{r\sin\partial+d\sin(\partial-\pi+L)}{r\cos\partial+d\cos(\partial-\pi+L)}\;, $$

where $r$ is the radius and $d$ is the length of the red line.

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    This solution is so utterly simple, but it baffled me for days, thank you very much!2012-09-27
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    @KorvinSzanto, the solution is clever, not so simple though!2012-09-27