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CBSE Class 12 Math 2018 Solved Paper

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Question : 26 of 29
Marks: +1, -0
Using integration, find the area of the region in the first quadrant enclosed by the x axis, the line y = x and the circle x2+y2x^2 + y^2 = 32
Solution:  
Given that y = x and x2+y2x^2 + y^2 = 32
Put y = x in x2+y2x^2 + y^2 = 32
x2+y2x^2 + y^2 = 32
2x22x^2 = 32
⇒ x = ± 4 = y
Hence, point s of intersection are A (4,4) and B (4,-4) .
Required shaded area
= 04\int\limits_{0}^{4} x dx + 432\int\limits_{4}^{\sqrt{32}} 32x2\sqrt{32-x^2} dx (Since Region in the first quadrant)
= (x24)04\left(\frac{x^2}{4}\right)_{0}^{4} +
[12(32x2)+12×32sin1(x32)]432\left[ \frac{1}{2} \left( \sqrt{32-x^2} \right) + \frac{1}{2} \times 32 \sin^{-1} \left( \frac{x}{32} \right) \right]_{4}^{\sqrt{32}}
= 4π sq . units
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