Problem 1
The circumference is the full perimeter around the circle. You can think of it as the combination of "circle" and "fence" to get "circumference", but there might be other tricks to remember the term.
Anyways, the formula to get the circumference of a circle is
C = 2*pi*r
In this case, r = 14 is our radius so,
C = 2*pi*r
C = 2*pi*14
C = 28pi .... exact circumference in terms of pi
We only want a portion of this circumference as shown by the piece of the circle darkened. The fractional portion we want is 135/360 of a circle. Divide the angle by 360 to get the fractional portion you want. If the angle was say 180 degrees, then 180/360 = 1/2 is the fractional portion.
So we take 135/360 and multiply it by the value of C found earlier
arc length = (fractional portion)*(circumference)
arc length = (135/360)*28pi
arc length = 10.5pi
That's the exact arc length in terms of pi. Use a calculator to find that
10.5pi = 32.9867228626929
Or you could use pi = 3.14 to say
10.5*pi = 10.5*3.14 = 32.97
Which is fairly close to what the calculator is saying
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<h3>Summary:</h3>
Exact arc length = 28pi
Approximate arc length (using calculator) = 32.9867228626929
Approximate arc length (using 3.14 for pi) = 32.97
Units are in feet
When I write "using calculator", I mean using the calculator's stored version of pi, instead of pi = 3.14
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Problem 2
We could use the same idea as problem 1, or we could use the formula below. The formula is just a quick way of encapsulating what I discussed earlier.
L = arc length
x = central angle
L = (x/360)*2*pi*r
L = (150/360)*2pi*13
L = (65/6)pi .... exact arc length
L = 34.0339204138894 .... approx arc length (using calculator)
L = 34.0166666666667 .... approx arc length (using 3.14 for pi)
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<h3>Summary:</h3>
Exact arc length = (65/6)pi
Approximate arc length (using calculator) = 34.0339204138894
Approximate arc length (using 3.14 for pi) = 34.0166666666667
Units are in meters
