trig_taylor.r2py

"""
<Program Name>
  trig.r2py

<Purpose>
  This is a script of some basic Trigonometric functions, and the
  distance calculation by geo coordinate
"""

dy_import_module_symbols("math.r2py")
pi = 3.14159265358979323846
e = math_e


# converts decimal degrees to radians
def deg2rad(deg):
  return (deg * pi / 180)

# converts radians to decimal degrees
def rad2deg(rad):
  return (rad * 180 / pi)


TERMS = 11

def factorial(x):
  result = 1 
  for num in range(x):
    result *= (num + 1)
  return result


def choose(x):
  numerator = 1.0
  denominator = 1.0
  for num in range(x+1, x * 2 + 1):
    numerator *= num
  for num in range(1, x+1):
    denominator *= num
  return numerator / denominator



def cos(x):
  taylorsum = 0.0
  for n in range(TERMS):
    taylorsum += (-1)**n * (x**(2.0*n) / factorial(2*n))
  return max(min(taylorsum, 1), -1)


def sin(x):
  return (1 - cos(x)**2)**0.5

def tan(x):
  return sin(x)/cos(x)


def asin(x):
  taylorsum = 0.0
  for n in range(TERMS):
    taylorsum += choose(n) * x ** (2 * n + 1) / (4 ** n * (2 * n + 1))
  return taylorsum


def acos(x):
  return  pi / 2 - asin(x)

def atan(x):
  return asin(x/(x ** 2 + 1) ** 0.5)

def atan2(y, x):
  if x == 0:
    if y > 0:
      result = pi/2
    elif y < 0:
      result = -pi/2
    #else:
      #error message
    return result

  result = atan(y/x)
  if x < 0:
    if y >= 0:
      result = result + pi
    else:
      result = result - pi
  return result


# -*- mode: python;-*-