CBSE Class 12 Math 2009 Solved Paper

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Question : 26
Total: 29
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 y2 = 4x and x2 = 4y
4
0
(2x.
x2
4
)
dx = [2
x
3
2
3
2
x3
12
]
04
=
32
3
16
3
=
16
3
sq units ………..(i)
Again, the area of the region OPQAO bounded by the curves x2 = 4y, x = 0, x = 4 and the x-axis,
4
0
x2
4
dx = [
x3
12
]
04
= (
64
12
)
=
16
3
sq units ……….(ii)
Similarly, the area of the region OBQRO bounded by the curve y2 = 4x, the y-axis, y = 0 and y = 4
4
0
y2
4
dy = [
y3
12
]
04
=
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
y2 = 4x and x2 = 4y divides the area of the square into three equal parts.
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