PerpPQ Definition

# The blue line in the above diagram is PerpPQ(P,Q) .

# Line through point Q perpendicular to the line joining
# point P and point Q.
# It uses the fact that the product of the slopes of perpendicular lines. is -1

PerpPQ:=proc(P,Q):

expand( (y-Q[2])*(P[2]-Q[2]) + (x-Q[1])*(P[1]-Q[1]) ):

end:

Definitions Theorems