AREA Definition

# Area of the triangle whose vertices are points A, B, and C

#Recall that a point is given by a list of length 2

AREA:=proc(A,B,C):

normal(expand(   (B[1]*C[2]-B[2]*C[1]-A[1]*C[2]+A[2]*C[1] -B[1]*A[2]+B[2]*A[1])/2   )):

end: