For x (- 2, 2 ), if y(x)= cosec x+ xcosec x x+ x 2x dx, and x ( 2 )-y(x)=0 then y ( 4 ) is equal to
- - 1 2 -1 ( 1 2 )
- -1 ( 1 2 )
- 12 -1 ( 1 2 )
- 1 2 -1 (- 12 )
Answer
(4) 1 2 -1 (- 12 )
Solution
Multiply numerator and denominator by x x:
Integrand = (1+ 2x) x1+ 4x
Put x=t: y= 1+t21+t4 dt= 1+ 1t2 (t- 1t )2+2 dt
Put t- 1t=u, (1+ 1t2 )dt=du:
y= duu2+2= 1 2 -1 ( t- 1t 2 )+C
x ( 2 )-: t 1, u 0 C=0
x= 4: t= 1 2, t- 1t=- 1 2
y ( 4 )= 1 2 -1 (- 12 )
Answer: (4)