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I am reading about the geometrical derivation of the centripetal acceleration formula. And the only thing I don't understand is the angles.

For example, here is a picture.

enter image description here

The assertion is that angle $BCD$ = $\theta$

However, I cannot understand this at all. The lines aren't parallel. There's no way they can prove this. What am I not understanding or missing here?

Jason
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1 Answers1

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Notice that $OACB$ is a 4 sided polygon, so all interior angles add up to $360^{\circ}$. We have that $\angle OAC=\angle OBC =90^{\circ}$. Hence $\angle ACB=180-\theta$ and hence $\angle BCD=\theta$.

BlackAdder
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