•Example

In[872]:=

xy = {x, y} ; area[{xn[1], yn[1]}, {xn[2], yn[2]}, {xn[3], yn[3]}] area[xy, {xn[2], yn[2]}, {xn[3], yn[3]}]

Out[873]=

1/2 (-xn[2] yn[1] + xn[3] yn[1] + xn[1] yn[2] - xn[3] yn[2] - xn[1] yn[3] + xn[2] yn[3])

Out[874]=

1/2 (-y xn[2] + y xn[3] + x yn[2] - xn[3] yn[2] - x yn[3] + xn[2] yn[3])

Converted by Mathematica  (March 7, 2003)