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I have trouble with this questions,

I don't get it, how can I express the letter with the angle, is it with the functions? Circle

Thanks for your help.

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up vote 0 down vote accepted

I don't know what they mean exactly by "the trigonometric ratios of $\theta$." But I can tell you that, since the radius has length 1, according to the figure, that $a=\sin\theta$, $d=\cos\theta$, and I'll let you take the rest from there. I wouldn't generally give that much info for what is obviously a homework problem, but it seems to me that the question is put poorly.

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Thanks @bob.sacamento Indeed, this way of asking troubled me... – Minimorum May 8 '14 at 22:38

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