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CBSE Class 12 Math 2009 Solved Paper

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Question : 26 of 29
Marks: +1, -0
Prove that the curves y² = 4x and x² = 4y divide the area of the square bonded by x = 0, x = 4, y = 4, and y = 0 into three equal parts.
Solution:  
The point of intersection of the
Parabolas y² = 4x and x² = 4y are (0, 0) and (4, 4)
Now, the area of the region OAQBO bounded by curves y2y^2 = 4x and x2x^2 = 4y
04(2xx24)\int\limits_{0}^{4} \left(2\sqrt{x} \cdot \frac{x^2}{4}\right) dx = [2x3/232x312]04\left[\frac{2x^{3/2}}{\frac{3}{2}} - \frac{x^3}{12}\right]_{0}^{4} = 323163\frac{32}{3} - \frac{16}{3} = 163\frac{16}{3} sq units ………..(i)
Again, the area of the region OPQAO bounded by the curves x2x^2 = 4y, x = 0, x = 4 and the x-axis,
04x24\int\limits_{0}^{4} \frac{x^2}{4} dx = [x312]04\left[\frac{x^3}{12}\right]_{0}^{4} = (6412)\left(\frac{64}{12}\right) = 163\frac{16}{3} sq units ……….(ii)
Similarly, the area of the region OBQRO bounded by the curve y2y^2 = 4x, the y-axis, y = 0 and y = 4
04y24\int\limits_{0}^{4} \frac{y^2}{4} dy = [y312]04\left[\frac{y^3}{12}\right]_{0}^{4} = 163\frac{16}{3} sq units ... (iii)
From (i), (ii), and (iii) it is concluded that the area of the region OAQBO = area of the region OPQAO = area of the region OBQRO, i.e., area bounded by parabolas
y2y^2 = 4x and x2x^2 = 4y divides the area of the square into three equal parts.
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