python08():
  Exercises for functions.

  Triangular number example:

  triangular_number(1) = 1
  triangular_number(10) = 55
  triangular_number(100) = 5050

  BMI example:

  bmi ( 100, 50 ) = 28.13061524500907
  bmi ( 150, 60 ) = 29.302724213551116
  bmi ( 200, 70 ) = 28.704709433682726
Help on function bmi in module my_library:

bmi(weight_lb, height_in)
    Purpose: bmi() computes the BMI (body mass index).
    
    Discussion: the BMI has a simple formula when the input is defined in metric units
    This program accepts data in English units (pounds and inches) and applies the
    correct unit conversions.  An "ideal" BMI is between 18.5 and 30.  Above 30 begins
    to count as "obese" and below 18.5 is considered "underweight".
    
    Example: bmi ( 150, 60 ) returns the value 29.30
    
    Modified: 12 May 2022
    
    Author: John Burkardt
    
    Reference:  https://en.wikipedia.org/wiki/Body_mass_index
    
    Input: 
      weight_lb, the weight in pounds.
      height_in, the height in inchdes.
      
    Output:
      value, the body mass index.


  Fahrenheit/Celsius example:

  f_to_c ( 40 ) = 4.444444444444445  = 04?
  f_to_c ( 61 ) = 16.11111111111111  = 16?
  f_to_c ( 82 ) = 27.77777777777778  = 28?
  f_to_c ( c_to_f ( -40 ) ) =  -40.0  = -40?
  f_to_c ( c_to_f (   0 ) ) =  0.0  =   0?
  f_to_c ( c_to_f ( 100 ) ) =  100.0  = 100?

  Compute coefficients of derivative of a polynomial.

  d = poly_dif ( [ 100, 50, 25, 10, 5, 2, 6 ] ):

  d =  [50. 50. 30. 20. 10. 36.]

  Fahrenheit/Kelvin example:

  f_to_k ( -40 ) = 233.14999999999998
  f_to_k (  32 ) = 273.15
  f_to_k ( 212 ) = 373.15
  k_to_f ( f_to_k ( -40 ) ) =  -40.0  = -40?
  k_to_f ( f_to_k (  32 ) ) =  32.0  =  32?
  k_to_f ( f_to_k ( 212 ) ) =  212.0  = 212?