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NCERT Class XII Mathematics Chapter - - Solutions

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Exercise - 7.11
By using the properties of definite integrals, evaluate the integrals in Exercises 208 to 225.
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Question : 223 of 271
Marks: +1, -0
∫0axx+a−xdx\int\limits_{0}^{a}\frac{\sqrt{x}}{\sqrt{x}+\sqrt{a-x}}dx
Solution:  
Let I=∫0axx+a−xdxI=\int\limits_{0}^{a}\frac{\sqrt{x}}{\sqrt{x}+\sqrt{a-x}}dx...(i)
I=∫0aa−xa−x+a−(a−x)dxI=\int\limits_{0}^{a}\frac{\sqrt{a-x}}{\sqrt{a-x}+\sqrt{a-(a-x)}}dx =∫0aa−xa−x+xdx=\int\limits_{0}^{a}\frac{\sqrt{a-x}}{\sqrt{a-x}+\sqrt{x}}dx...(ii)
Adding (i) and (ii), we get
2I=∫0ax+a−xx+a−xdx2I=\int\limits_{0}^{a}\frac{\sqrt{x}+\sqrt{a-x}}{\sqrt{x}+\sqrt{a-x}}dx =∫0a1⋅dx=[x]0a=a−0=a=\int\limits_{0}^{a}1\cdot dx=[x]_{0}^{a}=a-0=a
∴I=a2\therefore I=\frac{a}{2}
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