Determine the area bounded by the graph . If the answer is in the form , determine the value of .
Note: A scientific calculator is allowed, but please refrain from using a graphing calculator.
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The equation can be rewritten as ( ∣ y ∣ + 2 ) 2 + ( x − 4 ) 2 = 1 6 . If ∣ y ∣ is replaced with y , the equation would be a circle centered at ( 4 , − 2 ) . Because of the absolute value, the region of the circle below the x -axis is replaced with the region of the graph above the x -axis. In other words, the part of the graph above the x -axis is reflected over the x -axis, which means the total area is twice the area bound by the part of the graph above the x -axis and the line y = 0 .
We know that the radius is 4 so the graph never enters the 2nd or 3rd quadrant. This means the area above the x -axis is a circular cap with the base being the part of the x -axis contained within the circle. The distance of the chord that represents the part of the x -axis contained in the circle can be found by setting y = 0 , meaning x = 4 + 2 √ 3 and x = 4 − 2 √ 3 so the distance of the chord would be 4 √ 3 .
We can draw radii from ( 4 , − 2 ) to the endpoints of this chord and find the angle between the radii using the Law of Cosines since we know the radii are both 4 . The angle comes out to be 1 2 0 ˙ and the area of the circular cap would be 3 1 6 π − ( 0 . 5 ∗ 4 2 ∗ 0 . 5 ∗ sin 1 2 0 ) and multiplying this by 2 accounts for the reflection across the x -axis. The final area comes out to be 3 3 2 π − 8 √ 3 so ( a + b + c ) = 3 2 + 8 + 3 = 4 3 which is the final answer.