Programming Example: The Length of a Parabola Segment

Problem Statement

Given base b and height h, the length of a special segment on a parabola can be computed as follows:

Write a program to read in the values of base and height, and use the above formula to compute the length of the parabola segment. Note that both base and height values must be positive.


! -----------------------------------------------------------
!   Calculate the length of a parabola given height and base.                                         *
! -----------------------------------------------------------

PROGRAM  ParabolaLength

   REAL  :: Height, Base, Length
   REAL  :: temp, t

   WRITE(*,*)  'Height of a parabola : '
   READ(*,*)   Height

   WRITE(*,*)  'Base of a parabola   : '
   READ(*,*)   Base

! ... temp and t are two temporary variables

   t      = 2.0 * Height
   temp   = SQRT(t**2 + Base**2)
   Length = temp + Base**2/t*LOG((t + temp)/Base)

   WRITE(*,*)  'Height = ', Height
   WRITE(*,*)  'Base   = ', Base
   WRITE(*,*)  'Length = ', Length

END PROGRAM  ParabolaLength
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Program Output

 Height of a parabola :

 Base of a parabola   :

 Height = 100.
 Base   = 78.5
 Length = 266.149445

The input values for Height and Base are 100.0 and 78.5, respectively. The computed length is 266.149445.