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Integrals

Question
CBSEENMA12035789

Find the area bounded by the circle x2 + y2 = 16 and the line √3y=x in the first quadrant, using integration.

Solution

The area of the region bounded by the circle, x2+y2=16, x=√3y, and the x-axis is the area OAB.

Solving x2+y2=16 and x=√3y, we have

(√3y)2+y2=16
⇒3y2+y2=16
⇒4y2=16
⇒y2=4
⇒y=2
(In the first quadrant, y is positive)

When y = 2, x = 2√3

So, the point of intersection of the given line and circle in the first quadrant is (2√3,2).

The graph of the given line and circle is shown below:

Required area = Area of the shaded region = Area OABO = Area OCAO + Area ACB
Area OCAO = 12×2√3×2=2√3 sq units
Area space ABC space equals space integral subscript 2 square root of 3 end subscript superscript 4 space straight y space dx
space equals space integral subscript 2 square root of 3 end subscript superscript 4 square root of 16 minus straight x squared dx end root
space equals space open square brackets straight x over 2 square root of 16 minus straight x squared end root space plus 16 over 2 space sin to the power of negative 1 end exponent space straight x over 4 close square brackets subscript 2 square root of 3 end subscript superscript 4
space equals space open square brackets open parentheses 0 plus space 8 space sin to the power of negative 1 end exponent 1 close parentheses minus open parentheses fraction numerator 2 square root of 3 over denominator 2 end fraction space straight x space 2 space plus 8 space straight x space sin to the power of negative 1 end exponent fraction numerator square root of 3 over denominator 2 end fraction close parentheses close square brackets
space equals space 8 space straight x space straight pi over 2 minus 2 square root of 3 space minus 8 space straight x space straight pi over 3
space equals open parentheses fraction numerator 4 straight pi over denominator 3 end fraction minus 2 square root of 3 space close parentheses space sq space unit
therefore space Required space area space equals space open parentheses fraction numerator 4 straight pi over denominator 3 end fraction minus 2 square root of 3 close parentheses space plus 2 square root of 3 space equals space fraction numerator 4 straight pi over denominator 3 end fraction space sq space units

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