The central angle of an arc measures 12°. The radius of its circle is 30 inches. What is the length of the arc to the nearest quarter inch
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OpenStudy (anonymous):
1 in
6 1/4 in
37 1/2 in
94 1/4 in
OpenStudy (anonymous):
@Owlcoffee
OpenStudy (owlcoffee):
A central angle has the quality that is is equal the arc it intersects.
The definition of a central angle is that it's an angle, composed of two radiuses and the center of the circumference and is equal the arc it intersects.
|dw:1417916400648:dw|
\[<O=arc.AB\]
now, what we have to do, knowing that, is calculate the perimeter of the circle and sustract 12 from it.
OpenStudy (anonymous):
The perimeter of the circle ?
OpenStudy (anonymous):
@Owlcoffee
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OpenStudy (owlcoffee):
yes, it's calculated:
\[P_\circ =2 \pi r\]
OpenStudy (owlcoffee):
Does it specify the what arc they want you to calculate?
jimthompson5910 (jim_thompson5910):
You find the perimeter but you don't subtract 12 from it.
You find the perimeter and then multiply that perimeter (aka circumference) by 12/360
OpenStudy (owlcoffee):
Yes, I was doubting that method would work out.
thanks @jim_thompson5910
OpenStudy (anonymous):
30
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OpenStudy (anonymous):
@Owlcoffee
OpenStudy (anonymous):
or 94.2?
OpenStudy (anonymous):
@jim_thompson5910
OpenStudy (anonymous):
@GodlyMaths
jimthompson5910 (jim_thompson5910):
what circumference did you get?
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OpenStudy (anonymous):
6.28
jimthompson5910 (jim_thompson5910):
use C = 2*pi*r where r = 30 in this case
OpenStudy (anonymous):
188.4
jimthompson5910 (jim_thompson5910):
now multiply that by 12/360
jimthompson5910 (jim_thompson5910):
you are doing this because the arc is 12/360 of the circle's full perimeter
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OpenStudy (anonymous):
okay so i multiply 188.4 x 12 x 360 ? or 188.4 x 12/360?
jimthompson5910 (jim_thompson5910):
188.4 x 12/360
OpenStudy (anonymous):
6.28
jimthompson5910 (jim_thompson5910):
round that to the nearest quarter inch
OpenStudy (anonymous):
6 1/4?
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