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NDA 2019 Maths · Mathematics · Application of Integrals · hard

The area of the region enclosed by the parabolas y^2=4x and x^2=4y is

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The area of the region enclosed by the parabolas y2=4xy^2=4x and x2=4yx^2=4y is
  1. A. 83\frac{8}{3} sq. units
  2. B. 1616 sq. units
  3. C. 163\frac{16}{3} sq. units
  4. D. 323\frac{32}{3} sq. units
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Answer: (C) 163\frac{16}{3} sq. units

The parabolas meet at (0,0)(0,0) and (4,4)(4,4). Between x=0x=0 and 44, the upper curve is y=2xy=2\sqrt x and the lower is y=x24y=\frac{x^2}{4}. Area =∫04(2x−x24)dx=323−163=163=\int_0^4\left(2\sqrt x-\frac{x^2}{4}\right)dx=\frac{32}{3}-\frac{16}{3}=\frac{16}{3}. Using only the integral of 2x2\sqrt x gives the trap value 323\frac{32}{3}.
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