The area of the region, inside the circle and outside the parabola is:
- A
- B
- C
- D
The area of the region, inside the circle and outside the parabola is:
Correct answer:C
Standard Method
Given: The circle is and the parabola is . Find: The area of the region lying inside the circle and outside the parabola.
First, find the points of intersection by substituting into the circle:
Expanding,
So, the intersection points occur at and .
For , the upper half of the circle is
and the upper branch of the parabola is
Hence, the required area is
From the given solution, this evaluates to
Therefore, the required area is . The correct option is C.
Geometry and intersection interpretation
Given: The circle has center and radius , and the parabola is . Find: The area common to being inside the circle but outside the parabola.
The circle is centered on the positive -axis and the parabola opens to the right. After finding the intersections at and , the bounded part of the required region lies between these two curves over the interval .
Thus the area is obtained by integrating upper curve minus lower curve over the interval of intersection:
the solution concludes that this integral equals
So the correct option is C.
Using the whole circle area instead of the bounded region between the circle and parabola is incorrect, because the question asks only for the part inside the circle and outside the parabola. Set up the area as the difference of the two curves over the interval of intersection.
Finding intersection points incorrectly by solving only one equation or by algebraic expansion errors leads to wrong limits. Substitute into the circle carefully and use the limits to .
Subtracting the functions in the wrong order gives a negative area. Over the required interval, take the upper semicircle expression first and then subtract the upper branch of the parabola.
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