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Provide solution for RD Sharma Maths Class 12 Chapter 20 Areas of Bounded Region Exercise 20.3 question 13.

Answers (1)

Answer:

\begin{aligned} &{\left[\frac{4}{\sqrt{3}} a^{3 / 2}+\left[\frac{8 \pi}{3}-a \sqrt{\frac{16}{3}-a^{2}}-\frac{16}{3} \sin ^{1}-\left(\frac{\sqrt{3 a}}{4}\right)\right]\right] \text { square unit. }} \\ &\text { where } a=\frac{-9+\sqrt{273}}{9} \end{aligned}

Hint: Using the identity formula \int \sqrt{a^{2}-x^{2}} d x=\frac{x}{2} \sqrt{a^{2}-x^{2}}+\frac{a^{2}}{2} \sin -{ }^{1} \frac{x}{a}+c . .

Given: Here we know that R = {(x, y): y^2 \leq 3x, 3x^2 + 3y^2\leq 16}

Solution:

Here we know that R = {(x, y): y^2 \leq 3x, 3x^2 + 3y^2\leq 16}

We can write it as

R = {(x, y): y^2 \leq 3x} \cap {(x, y): 3x^2 + 3y^2 \leq 16} = R_1 \cap R_2

 Here R_1 = {(x, y): y^2 \leq 3x}  which represents the region inside the parabola, y2 = 3x with vertex (0, 0) and x-axis as it axis

R = {(x, y): 3x^2 + 3y^2 \leq 16}  represents the interior of 3x^2 + 3y^2 = 16 circle having (0, 0) as centre and \frac{4}{\sqrt{3}} as radius

So the region R which is intersection of points R1 and R2 is shaded in the figure

 3x^2 + 3y^2 = 16 …… (1)

y^2 = 3x…… (2)

Solving both the equations

 3x2 + 9x – 16 = 0

 So we get

x = \frac{(-9 \pm \sqrt{2}73)}{}6

 Here x = \frac{(-9 \pm \sqrt{2}73)}{}6  is the rejecting negative value

 Substituting y = 0 in equation (1)

 x=\frac{4}{\sqrt{3}}

 We know that the circle (1) cuts x-axis at P \left (\frac{4}{\sqrt{3}},0 \right ) and P’ (\left (-\frac{4}{\sqrt{3}},0 \right )

 So the required area can be written as

 Required area = 2 [area of ODPAO] = 2 [area of ODAO + area of ADPA] .

\text { Re quired area }=2\left[\int_{0}^{a} \sqrt{3 x} d x+\int_{a}^{4, \sqrt{\beta}} \sqrt{\sqrt{3}-x^{2}} d x\right]

Intergrating w.r.t

=2\left(\sqrt{3}\left[\frac{x^{3 / 2}}{3 / 2}\right]_{0}^{a}+\left[\frac{x}{2} \sqrt{\frac{16}{3}-x^{2}}+\frac{16}{3} \sin ^{-1}\left(\frac{x}{4 / \sqrt{3}}\right)\right]_{a}^{4 / \sqrt{s}}\right)

Substituting the value of x

\begin{aligned} &{\left[\frac{4}{\sqrt{3}} a^{3 / 2}+\left[\frac{8 \pi}{3}-a \sqrt{\frac{16}{3}-a^{2}}-\frac{16}{3} \sin ^{1}-\left(\frac{\sqrt{3 a}}{4}\right)\right]\right] \text { square unit. }} \\ &\text { where } a=\frac{-9+\sqrt{273}}{9} \end{aligned}

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