Q69 / 200 · WBJEE 2014 · Mathematics
The area of the region bounded by the curves $y=x^{2}$ and $x=y^{2}$ is
- Correct answerA$1 / 3$
- B$1 / 2$
- C$1 / 4$
- D3
Solution
Given curves are $y=x^{2}$ and $x=y^{2}$, which is the form of parabola.
The point of intersection, $x=\left(x^{2}\right)^{2}$$
\begin{array}{l}
\Rightarrow \quad x=x^{4} \Rightarrow x\left(1-x^{3}\right)=0 \\
\Rightarrow \quad x=0 \text { and } 1=x^{3} \\
\Rightarrow \quad x=0 \text { and } x=1 \\
\text { When } x=0, \text { then } y=0 \\
\text { When } x=1, \text { then } y=1^{2}=1
\end{array}
$
$\therefore$ The point of intersection is (0,0) and (1,1)
$\therefore$ Area of shaded region
$$
\begin{array}{l}
=\int_{0}^{1}\left(y_{2}-y_{1}\right) d x \\
=\int_{0}^{1}\left[\sqrt{x}-x^{2}\right] d x=\left[\frac{x^{3 / 2}}{3 / 2}-\frac{x^{3}}{3}\right]_{0}^{1} \\
=\frac{2}{3}(1)^{3 / 2}-\frac{(1)^{3}}{3}-0-0 \\
=\frac{2}{3}-\frac{1}{3}=\frac{1}{3} \mathrm{sq} \text { units }
\end{array}
$$
The point of intersection, $x=\left(x^{2}\right)^{2}$$
\begin{array}{l}
\Rightarrow \quad x=x^{4} \Rightarrow x\left(1-x^{3}\right)=0 \\
\Rightarrow \quad x=0 \text { and } 1=x^{3} \\
\Rightarrow \quad x=0 \text { and } x=1 \\
\text { When } x=0, \text { then } y=0 \\
\text { When } x=1, \text { then } y=1^{2}=1
\end{array}
$
$\therefore$ The point of intersection is (0,0) and (1,1)
$\therefore$ Area of shaded region
$$
\begin{array}{l}
=\int_{0}^{1}\left(y_{2}-y_{1}\right) d x \\
=\int_{0}^{1}\left[\sqrt{x}-x^{2}\right] d x=\left[\frac{x^{3 / 2}}{3 / 2}-\frac{x^{3}}{3}\right]_{0}^{1} \\
=\frac{2}{3}(1)^{3 / 2}-\frac{(1)^{3}}{3}-0-0 \\
=\frac{2}{3}-\frac{1}{3}=\frac{1}{3} \mathrm{sq} \text { units }
\end{array}
$$Hence, the correct answer is option: 'A'.