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Explain solution RD Sharma Class 12 Chapter 20 Areas of Bounded Regions exercise 20.3 question 37 Maths.

Answers (1)

Answer:

\frac{32\pi}{3}-\frac{4}{\sqrt{3}} \; \text{sq.units} 

Hints:

Given: Equation of circle x^2+y^2=32  exterior to parabola y^2=6x

Solution: First finding intersection point by solving the equation of two curves

\begin{aligned} &x^{2}+y^{2}=16 \ldots \text { (i) } \\ &\text { and } y^{2}=6 x \ldots \text { (ii) } \\ &\Rightarrow x^{2}+6 x=16 \\ &\Rightarrow x^{2}+6 x-16=0 \end{aligned}

\begin{aligned} &\Rightarrow x^{2}+8 x-2 x-16=0 \\ &\Rightarrow x(x+8)-2(x+8)=0 \\ &\Rightarrow(x+8)(x-2)=0 \\ & x=-8 \end{aligned}

(not possible y^2 cannot be -ve )

Or  x=2    (only allowed value)

y=\pm 2\sqrt{3}

\begin{aligned} &A_{1}=\int_{0}^{2} \sqrt{6 x} d x=\left[\frac{\sqrt{6} x^{\frac{3}{2}}}{\frac{3}{2}}\right]_{0}^{2} \\ &=\frac{2 \sqrt{6}}{3} \times 2^{\frac{3}{2}}=\frac{2 \sqrt{3} \times \sqrt{2}}{3} \times 2 \sqrt{2} \\ &=\frac{8}{\sqrt{3}} \text { sq.units } \end{aligned}

\begin{aligned} &A_{2}=\int_{2}^{4}\left(\sqrt{16-x^{2}}\right) d x=\left[\frac{x}{2} \sqrt{16-x^{2}}+\frac{16}{2} \sin ^{-1} \frac{x}{4}\right]_{2}^{4} \\ &=0+8 \sin ^{-1}-8 \sin ^{-1} \frac{1}{2}-\sqrt{16-4} \\ &=8 \times \frac{\pi}{2}-8 \times \frac{\pi}{6}-\sqrt{12} \\ &=4 \pi-\frac{4 \pi}{3}-\sqrt{12} \\ &=\frac{8 \pi}{3}-\sqrt{12} \text { sq.units } \end{aligned}

\begin{aligned} &\text { Area }=2\left(A_{1}+A_{2}\right) \\ &=2\left(\frac{8}{\sqrt{3}}+\frac{8 \pi}{3}-\sqrt{12}\right) \\ &\text { Required area }=\pi \times 16-\frac{16 x}{3}+4 \sqrt{3}-\frac{16}{\sqrt{3}} \\ &=\frac{32 \pi}{3}-\frac{4}{\sqrt{3}} \end{aligned}\frac{32\pi}{3}-\frac{4}{\sqrt{3}} \; \text{sq.units}

Therefore, the area of the circle is \frac{32\pi}{3}-\frac{4}{\sqrt{3}} \; \text{sq.units} 

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