A circle's center is at (9,2) and it passes through (5,2). What is the length of an arc covering π3 radians on the circle?

1 Answer
May 24, 2018

4π3

Explanation:

The distance between the center and any point on the circle is the radius. From the 2 points given in the description, we can determine that the radius r=95=4
More formally, the distance between any two points is:
d=(y2y1)2+(x2x1)2
In this case: r=(22)2+(95)2=42=4

The circumference of this circle is C=2πr=8π

The length of the arc is a portion of the total circumference. Since the total arc around the whole circle is 2π, the proportion of the arc is π32π=16 of the total circumference.

So, the length of the arc covering π3 radians is (16)C,
that is:
(16)8π=4π3