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Please look at the diagram:


I know $D$, $\alpha$ and $\theta$. I also know the $a/b$ ratio of $k$. I don't know $c$. Can I find out $a$ or $b$ or $a+b$?

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It would have been good style to mention this directly related question:… to avoid unnecessary duplication of efforts. – joriki Aug 25 '11 at 8:04
sorry this is a different question.. they may look similar but nothing is far from truth.. – Frank Aug 25 '11 at 8:25
I can see it's a different question; otherwise I would have voted to close it as a duplicate. Nevertheless it's clear that some insight might be gained from answers to the other question, and there's no reason not to include a link. – joriki Aug 25 '11 at 8:30
What is $\alpha$? An angle? – Peter Taylor Aug 25 '11 at 8:57
α is the angle.. Sorry it wasn't clear. – Frank Aug 25 '11 at 9:03
up vote 3 down vote accepted

This is a slightly different question to this one. But the answer is the same: it is not possible to determine $a$ or $b$ or $a+b$. Look at this figure:

enter image description here

We can move the red lines anywhere in the $\theta$ cone without changing $\alpha$ and $k=a/b$. But $a$ and $b$ are changed.

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Thanks for the answer.. It is clear this is not possible. – Frank Aug 25 '11 at 9:25

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