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The area enclosed by \mathrm{y^{2}=8 x \: and \: y=\sqrt{2} x} that lies outside the triangle formed by \mathrm{y=\sqrt{2} x, x=1, y=2 \sqrt{2},} is equal to:

Option: 1

\frac{16 \sqrt{2}}{6}


Option: 2

\frac{11 \sqrt{2}}{6}


Option: 3

\frac{13 \sqrt{2}}{6}


Option: 4

\frac{5 \sqrt{2}}{6}


Answers (1)

best_answer

Point of intersection of  \mathrm{y=\sqrt{2}x} and  \mathrm{y^{2}=8x}

\mathrm{\Rightarrow(\sqrt{2} x)^{2}=8 x \Rightarrow 2 x^{2}=8 x \Rightarrow x=0,4} \\

\mathrm{\Rightarrow y=\sqrt{2} \cdot 4=4 \sqrt{2}} \\

\mathrm{\text { At } x=1 \Rightarrow y^{2}=8 x \Rightarrow y^{2}=8 \Rightarrow y=2 \sqrt{2}}

 

We need shaded area

\mathrm{\left(\text { As } y^{2}=8 x \Rightarrow y=2 \sqrt{2 x}\right)}\\

\mathrm{=\int_{0}^{4}(2 \sqrt{2 x}-\sqrt{2} x) d x-\frac{1}{2} \cdot \sqrt{2} \cdot 1}\\

\mathrm{=\left.2 \sqrt{2} \cdot \frac{x^{3 / 2}}{3 / 2}\right|_{0} ^{4}-\left.\sqrt{2} \cdot \frac{x^{2}}{2}\right|_{0} ^{4}-\frac{1}{\sqrt{2}}}\\

\mathrm{=\frac{8 \sqrt{2}}{3}-\frac{1}{\sqrt{2}}=\frac{16 \sqrt{2}-3 \sqrt{2}}{6}=\frac{13 \sqrt{2}}{6} }

Hence the answer is option 3.

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Gunjita

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