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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 : 102 of 271
Marks: +1, -0
x+2x2−1\frac{x+2}{\sqrt{x^2-1}}
Solution:  
Let I=∫x+2x2−1dxI=\int \frac{x+2}{\sqrt{x^2-1}}dx
=∫xx2−1dx+∫2x2−1dx=I1+I2(say)=\int \frac{x}{\sqrt{x^2-1}}dx + \int \frac{2}{\sqrt{x^2-1}}dx = I_1 + I_2 (\text{say})
⇒I=I1+I2\Rightarrow I = I_1 + I_2 ... (i)
Now, I1=∫xx2−1dxI_1=\int \frac{x}{\sqrt{x^2-1}}dx
Put x2−1=t⇒2xdx=dtx^2 - 1 = t \Rightarrow 2x dx = dt
I1=12∫dtt=12×t1/21/2+C1I_1=\frac{1}{2} \int \frac{dt}{\sqrt{t}} = \frac{1}{2} \times \frac{t^{1/2}}{1/2} + C_1
=t+C1=x2−1+C1= \sqrt{t} + C_1 = \sqrt{x^2-1} + C_1 ... (ii)
and, I2=∫2x2−1dxI_2=\int \frac{2}{\sqrt{x^2-1}}dx =2log⁡∣x+x2−1∣+C1= 2 \log |x + \sqrt{x^2-1}| + C_1... (iii)
From (i), (ii) and (iii), we get
I=x2−1+2log⁡∣x+x2−1∣+CI = \sqrt{x^2-1} + 2 \log |x + \sqrt{x^2-1}| + C
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