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CBSE Class 12 Math 2013 Solved Paper
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Question : 25 of 29
Marks:
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Using integration, find the area bounded by the curve = 4y and the line x = 4y – 2. OR Using integration, find the area of the region enclosed between the two circles = 4 and = 4.
Solution:
The shaded area OBAO represents the area bounded by the curve = 4y and line x = 4y – 2.
Let A and B be the points of intersection of the line and parabola. Co-ordinates of point A are . Co-ordinates of point B are (2, 1). Area OBAO = Area OBCO + Area OACO … (1) Area OBCO = dx - dx = - = (2 + 4) - = = Area OACO = dx - dx = - = - = - = = Therefore, required area = = sq. units OR Given equations of the circles are = 4 ... (1) = 4 ... (2) Equation (1) is a circle with centre O at the origin and radius 2. Equation (2) is a circle with centre C (2, 0) and radius 2. Solving (1) and (2), we have: = - 4x + 4 + = x = 1 This gives y = Thus, the points of intersection of the given circles are A (1 , and A' (1 , - ) as shown in the figure.
Required area = Area of the region OACA'O = 2 [area of the region ODCAO] = 2 [area of the region ODAO + area of the region DCAD] = 2 = 2 [ dx + dx] = 2


+ =
+ = + = - 2
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