LM

In the circle above, PQ is parallel to diameter OR, and OR has length 18. What is the length of minor arc PQ?
A. \(2\pi\)
B. \(\frac{9\pi}{4}\)
C. \(\frac{7\pi}{2}\)
D. \(\frac{9\pi}{2}\)
E. \(3\pi\)
First, since PQ is parallel to diameter OR, we know that arc PO = arc QR.
So, we can apply a circle property that says inscribed angles holding/containing arcs (or chords) of equal length must have the same angle measurement.

This means angle QOR must also be
35°Next, we'll apply the following property:

The above property tells us that, if an inscribed angle and a central angle are holding/containing the same arc (or chord), then the central angle will be TWICE the inscribed angle
So, if we take our given diagram, and add a line from the center to point Q...

....then the central angle holding/containing arc QR must be
70°We can apply the same logic to conclude....

...that the central angle holding/containing arc PO must be
70° Finally, since angles on a line must add to 180°,

....the missing angle here is
40°This means the length of minor arc PQ = 40/360 of the circle's circumference
The circumference of a circle = (pi)(diameter), and we're told that diameter OR has length 18.
So.....
The length of minor arc PQ = (40/360)(pi)(18)
= (1/9)(pi)(18)
= (18pi)/(9)
= 2pi
Answer: A
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