SOLUTION: Im not sure what formula to use for this problem Find the diameter of a circle that has an arc length of 36.90 cm and a central angle of 128 degrees 18 minutes. Round to 1 decim

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Question 1094939: Im not sure what formula to use for this problem
Find the diameter of a circle that has an arc length of 36.90 cm and a central angle of 128 degrees 18 minutes. Round to 1 decimal place.
Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
pi%2Ad formula for circumference; d for diameter

pi%2Ad%2A%28128.3%2F360%29=36.9

d=36.9%28360%2F128.3%29%281%2Fpi%29

d=33

Answer by ikleyn(52787) About Me  (Show Source):
You can put this solution on YOUR website!
.
Use the formula 


S = r%2Aalpha   (1)


for the arc length S, where "r" is the circle radius and alpha is the central angle in radians.


To use it, you need first to convert 128 degs 18 minutes to radians.


128 degs 18 minutes = 128*60 + 18 minutes = 7698 minutes.


2pi radians = 360 degs = 360*60 = 21600 minutes.


So, 128 degs and 18 nimutes = %282pi%29%2A%287698%2F21600%29 = 2.2381 radians.


So, your equation (1) now becomes

36.90 = 2.2381*r.


From it,  calculate r = 36.90%2F2.2381.


Then double your "r" to get he diameter.