new_contents: """ answer to """
  import numpy as np
  
  
  # terminiology: 
  # - segment are prefixed by `s` and followed by upper case nodes: e.g. `sAB` is the length of the semgnet from A to B
  # - angles are prefixed with `ang` and followed by upper case nodes: e.g. `angABC` is the angle between A, B, and C
  # - area are prefixed with `area` and followed by upper case ndes: e.g. `areaABC` is the area comprised between nodes A, B, and C
  # 
  # new defintions:
  # - we define a new node H, between A and B so that angAHC = angDHC = 90 deg
  
  
  ## helper function to convert ang to rad and reverse
  def angToRad(ang):
    return ang*np.pi/180
  
  def radtoAng(rad):
    return rad/np.pi*180
  ## end helper
  
  # var definition
  angCAD = angToRad(80)
  angDCB = angToRad(25)
  
  # var from the exercise
  sAB = 4.9
  sAD = 3.8
  
  # get height length
  sHC = sAB * np.sin(angCAD)
  # get distance from A to H
  sAH = sAB * np.cos(angCAD)
  # get distance from H to D
  sHD = sAD - sAH
  
  # get angle HCD
  angHCD = np.arctan(sHD / sHC)
  # get angle HCB
  angHCB = angHCD + angDCB
  
  # get HB
  sHB = sHC * np.tan(angHCB)
  # get distance from A to B
  sAB = sAH + sHB
  
  # get two triangles areas
  areaACD = sHC * sAD / 2
  areaACB = sAB * sHC / 2
  
  # get asked area
  areaDCB = areaACB - areaACD
  
  print areaDCB
subject: add quora calculation