Sum of the arcs

dragonrider

New member
Joined
Oct 12, 2014
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18
circle.jpg
"In the figure above, lines AC and BD are diameters of the circle, which has a radius of 9. What is the sum of the lengths of arcs AB and CD?"
(I cannot find the pi symbol so I will just use the word)
a. 2pi
b. 3pi
c. 4pi
d. 6pi
e. 8pi

I know that angle BEC is also 140 degress, which makes angles BEA and CED 40 degress, and that means arcs AB and CD are also 40 degrees. How do I find their lengths?
 
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