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∫dx9x-4x2 equals: - Mathematics

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Question

`int dx/sqrt(9x - 4x^2)` equals:

Options

  • `1/9  sin^-1 ((9x - 8)/8) + C`

  • `1/2  sin^-1 ((8x - 9)/9) + C`

  • `1/3  sin^-1 ((9x - 8)/8) + C`

  • `1/2  sin^-1 ((9x - 8)/9) + C`

MCQ

Solution

`1/2  sin^-1 ((8x - 9)/9) + C`

Explanaton:

Let `I = int  dx/sqrt(9x^2 - 4x^2)`

`= 1/2 int  dx/sqrt(9/4  x - x^2)`

`= 1/2 int dx/(sqrt(- (x^2 - 9/4  x)))`

`= 1/2 dx/sqrt(- (x^2 - 9/4 + 81/64) + 81/64)`

`= 1/2 int dx/sqrt(81/64 - (x - 9/8)^2)               ... [because int 1/(a^2 - x^2)  dx = sin^-1 x/a]`

`= 1/2  sin^-1 ((x - 9/8)/(9/8)) +C`

`= 1/2  sin^-1 ((8x - 9)/9) + C`

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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 25 | Page 316
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