If 32x+ 32x 3x 3x (x- ) dx =A x- +B - x+C, where C is the integration constant, then AB is equal to
- 2
- 8 cosec(2 )
- 4 cosec(2 )
- 4
Answer
(2) 8 cosec(2 )
Solution
(x- )= x - x ; split the integral into two parts:
I1= 3/2x dx 3/2x 3/2x x x - = 2x dx x -
I2= 3/2x dx 3/2x 3/2x x - x= cosec2x dx - x
∵ f'(x) f(x)dx=2 f(x), with ddx( x )= 2x and ddx(- x)= cosec2x:
I= 2 x-
+ 2 - x+C
A=2 , B=2 cosec
AB= 4 = 8 2 =8 cosec(2 )
Answer: (2)