Bisection Method

Consider finding the root of  f(x) = Cos[x] – x . Let ε_step = 0.01 ,  ε_abs = 0.001 and start with the interval [1.0 ,  0.5] .

Program Bisection_method

    Implicit none

    Real :: a , b , f , c , error

    

Write( * , * ) " Enter numbers between which the root is to be found : "   !(Can be change)

      10 read ( * , * ) a , b

 Write ( * , 61 ) " Input error value : "    !(Can be change)

       61 Format ( / , / , a18 )

        Read ( * , * ) error

     

  15 If ( f ( a ) * f ( b ) . lt . 0 )then

            c = ( a+b ) / 2.0

         else

  Write ( * , 62 ) " There is no zeros in this interval. Try with  another value of a & b "

       62 Format  ( / , / , a65 )

           go to 10

        Endif

        if ( f (a) * f (c) . lt . 0) then

            b = c

           else

          a = c

        Endif

       if ( abs (b-a) . gt . error ) goto 15

       write ( * , 63 ) " The approximate root of the function is : " , c

           63 Format ( / , / , a42 , f12.9 )

        end

    function f (x)

            implicit none

            real : : f , x

            f = cos (x) - x   !(Can be change)

    end function

Input ::

Output : :