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Integrate the function x+24x-x2 - Mathematics

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Question

Integrate the function `(x + 2)/sqrt(4x - x^2)`

Sum

Solution

Let `I = int (x + 2)/sqrt(4x - x^2)  dx`

`= int (x + 2)/sqrt(- (x^2 - 4x + 4) + 4)  dx`

`= int (x + 2)/sqrt(4 - (x - 2)^2)   dx`

`= (x - 2 + 4)/sqrt(4 - (x - 2)^2)   dx`

`= int (x - 2)/sqrt(4 - (x - 2)^2)   dx + 4  int 1/sqrt(4 - (x - 2)^2)   dx`

Let `I = I_1 + 4sin^-1 ((x - 2)/2) + C_1`          .....(i)

Where `I_1 = int (x - 2)/ sqrt (4 - (x - 2)^2)dx`

Put 4 - (x - 2)2 = t 

-2 (x - 2) dx = dt

`I_1 = 1/2 int dt/ sqrt ((2)^2 - t)`

`1/2 int dt/ sqrt (4 - t)`

`1/2 [(4 - t)^(-1/(2+1))/-(-1/2 + 1)] + C_2`

`= -sqrt ((4 - t)) + C_2`

`= - sqrt (4 - (x - 2)^2) + C_2`

`= - sqrt (4 - x^2 - 4 + 4x) + C_2`

`= - sqrt (4x - x^2) + C_2`                      ....(ii)

`I = - sqrt (4x - x^2) + 4sin^-1 ((x - 2)/2) + C`        ... [from (i) and (ii)]

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Chapter 7: Integrals - Exercise 7.4 [Page 316]

APPEARS IN

NCERT Mathematics [English] Class 12
Chapter 7 Integrals
Exercise 7.4 | Q 20 | Page 316
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