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  1. program r_f
  2.     implicit none
  3.     real :: p,q,eps,x,x1,fp,fq,fx
  4.     integer :: choice,i,max_i
  5.  
  6.     print*,"Enter a, b, epscilon, max_iteration"
  7.     read*, p, q, eps, max_i
  8.     print*,"Choose : 1 =Bisection, 2 = Newton, 3=Iteration, 4= Regula Falsi"
  9.     read*, choice
  10.     select case(choice)
  11.         case(1)
  12.             do i=1,max_i
  13.                 x = (p+q)/2.0
  14.                 fp = f(p); fq=f(q); fx=f(x)
  15.                 if(abs(fx)<eps) exit
  16.                 if(fp*fx<0) then
  17.                     q=x
  18.                 else
  19.                     p=x
  20.                 end if
  21.             end do
  22.             print*,"Root(Using Bisection) = ", x
  23.  
  24.         case(2)
  25.             x = (p+q)/2.0
  26.             do i=1,max_i
  27.                 x1 = x - f(x)/df(x)
  28.                 if(abs(x1-x)<eps) exit
  29.                 x = x1
  30.             end do
  31.             print*,"Root(Using Newton Raphson) = ", x
  32.  
  33.         case(3)
  34.             x = (p+q)/2.0
  35.             do i=1,max_i
  36.                 x1 = g(x)
  37.                 if(abs(x1-x)<eps) exit
  38.                 x = x1
  39.             end do
  40.             print*,"Root(Using Iteration) = ", x
  41.  
  42.         case(4)
  43.             fp=f(p);fq=f(q)
  44.             do i=1,max_i
  45.                 x = (p*fq-q*fp)/(fq-fp)
  46.                 fx=f(x)
  47.                 if(abs(x1-x)<eps) exit
  48.                 if(fp*fx<0) then
  49.                     q = x ; fq=fx
  50.                 else
  51.                     p = x
  52.                     fp=fx
  53.                 end if
  54.             end do
  55.             print*,"Root(Using Regula Falsi) = ", x
  56.     end select
  57. contains
  58.     real function f(x)
  59.         real, intent(in) :: x
  60.         f = x*x - 4.0
  61.     end function
  62.  
  63.     real function df(x)
  64.         real, intent(in) :: x
  65.         df = x*2.0
  66.     end function
  67.  
  68.     real function g(x)
  69.         real, intent(in) :: x
  70.         g = sqrt(4.0)
  71.     end function
  72. end program r_f
Success #stdin #stdout 0.01s 5288KB
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stdout
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 Enter a, b, epscilon, max_iteration
 Choose : 1 =Bisection, 2 = Newton, 3=Iteration, 4= Regula Falsi
 Root(Using Bisection) =    2.00000000
https://ideone.com/qw91DG
language:
Fortran (gfortran 8.3)
created:
2 days ago
visibility:
public

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