SOLUTION: A goat is tied outside a triangular fenced garden at point A. The sides of the fence are AB = 8 m, BC = 9 m, and CA = 12 m. If the rope with which the goat is tied is 14 m long, fi

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Question 1153288: A goat is tied outside a triangular fenced garden at point A. The sides of the fence are AB = 8 m, BC = 9 m, and CA = 12 m. If the rope with which the goat is tied is 14 m long, find the area over which the goat can graze outside the fence.
A.597.34 m2
B.565.87 m2
C.532.64 m2
D.500.32 m2

Answer by Edwin McCravy(20056)   (Show Source): You can put this solution on YOUR website!
The figure below is drawn to scale.  The red line is the rope, with 
the goat pulling it tight.  The circle has center A and radius 14 m.



The goat can graze anywhere in the circle except in the triangle and
in the area marked with an X in the figure below:



The desired area consists of three sectors.
1. The big sector whose center is A and has radius 14 m. Its
central angle is 360°-A 
2. The smallest sector whose center is C and has radius 2 m. Its
central angle is 180°-C.  
3. The next to smallest sector whose center is B and has radius 6 m.  
We will need the exterior angle at B to calculate its area. That will
be the sum of the two remote interior angles, A+C

We find all three angles of the triangle using the law of cosines.



The formula for the area of a sector is 



The area of the big sector: Its radius is r = 14 m. 
Its central angle is θ = 360°-A = 360°-48.58881136° = 311.4111886°.


The area of the smallest sector: Its radius is r = 2 m. 
Its central angle is θ = 180°-C = 180°-41.80907919° = 138.1909208°.


The area of the next to smallest sector: Its radius is r = 6 m. 
Its central angle is θ = A+C = 48.58881136° + 41.80907919° = 90.39789055°


Finally we add the three sectors together to get the entire grazing area:

532.6447557 + 4.823773129 + 28.39933489 = 565.8678637 m².

The correct answer is B.

Edwin

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