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NCERT Class XII Mathematics Chapter - - Solutions

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Exercise - 7.4
Integrate the functions in Exercises 86 to 108.
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Question : 105 of 271
Marks: +1, -0
x+24x−x2\frac{x+2}{\sqrt{4x-x^2}}
Solution:  
Let I=∫x+24x−x2dxI=\int\frac{x+2}{\sqrt{4x-x^2}}dx
=∫x+24−(x2−4x+4)dx=\int\frac{x+2}{\sqrt{4-(x^2-4x+4)}}dx
=∫(x−2)+44−(x−2)2dx=\int\frac{(x-2)+4}{\sqrt{4-(x-2)^2}}dx
=∫x−24−(x−2)2dx+4∫dx4−(x−2)2=\int\frac{x-2}{\sqrt{4-(x-2)^2}}dx+4\int\frac{dx}{\sqrt{4-(x-2)^2}}
Let I=I1+4sin⁡−1(x−22)+C1I=I_1+4\sin^{-1}\left(\frac{x-2}{2}\right)+C_1 ... (i)
where I1=∫x−24−(x−2)2dxI_1=\int\frac{x-2}{\sqrt{4-(x-2)^2}}dx
Put (x−2)2=t(x-2)^2=t ⇒2(x−2)dx=dt\Rightarrow 2(x-2)dx=dt
I1=12∫dt(2)2−tI_1=\frac{1}{2}\int\frac{dt}{\sqrt{(2)^2-t}}
=12∫dt4−t=\frac{1}{2}\int\frac{dt}{\sqrt{4-t}}
=12[(4−t)−12+1−(−12+1)]+C2=\frac{1}{2}\left[\frac{(4-t)^{-\frac{1}{2}+1}}{-\left(-\frac{1}{2}+1\right)}\right]+C_2
=−4−t+C2=-\sqrt{4-t}+C_2
=−4−(x−2)2+C2=-\sqrt{4-(x-2)^2}+C_2
=−4−x2−4+4x+C2=-\sqrt{4-x^2-4+4x}+C_2
=−4x−x2+C2=-\sqrt{4x-x^2}+C_2 ..(ii)
I=−4x−x2+4sin⁡−1(x−22)+CI=-\sqrt{4x-x^2}+4\sin^{-1}\left(\frac{x-2}{2}\right)+C [from (i) and (ii)]
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