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vivek.kapoor83
- Legendary Member
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- Joined: Mon Aug 04, 2008 1:56 am
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Seems these triangle/circle relationships are being discussed in a few posts.
There are a few ways to get to an answer here, but in any case, if you need the length of an arc, you need the angle it makes at the center of the circle. So a useful first thing to do here is to connect P and Q to the center (which I'll call A). Now, angle PRO is exactly half of angle PAO (a fact I just proved in a different thread), so PAO is 70 degrees, and by symmetry, QAR is 70 as well. That makes the angle we want, angle PAQ, 40 degrees (because PAO, PAQ and QAR form a straight line and must add to 180). Once you know the angle, the rest of the problem is straightforward.
