### Passage V
(Q. Nos. 58 to 60)
Let y=∫u(v)v(x)f(t)dt , let us define dxdy as dxdy=v′(x)f2(v(x))−u′(x)f2(u(x)) and the equation of the tangent at (a,b) and y−b=(dxdy)(a,b)(x−a) .
If f(x)=∫1xet1/2(1−t2)dt , then dxdf(x) at x=1 is
a. 0
b. 1
c. 2
d. -1