1 program trapezoidh3p31
  2 implicit none
  3
  4 double precision :: a,b,h,pi,u,ans,f,iter
  5 integer :: i
  6
  7 pi=4*atan(1.0)
  8 a=0.0d0
  9 b=sqrt(2.0d0)
 10 iter=68659
 11 h=(b-a)/iter
 12 ans=0.0d0
 13 u=a
 14
 15 ans=ans+(2.0d0/sqrt(pi))*f(a)
 16 ans=ans+(2.0d0/sqrt(pi))*f(b)
 17 do i=1,iter-1
 18    u=u+h
 19    ans=ans+2*(2.0d0/sqrt(pi))*f(u)
 20 end do
 21 ans=(h/2.0d0)*ans
 22 print* , "Answer is:"
 23 print* , ans
 24 stop
 25 end
 26
 27
 28
 29 double precision function f(u)
 30 implicit none
 31
 32 double precision :: u
 33
 34 f=exp(-u**2)
 35
 36 return
 37 end