1. determinants

prove that (x1,y1), (x2,y2) and (x3,y3) are collinear pts iff
determinant :
x1 y1 1
x2 y2 1
x3 y3 1 is zero

2. Originally Posted by alexandrabel90
prove that (x1,y1), (x2,y2) and (x3,y3) are collinear pts iff
determinant :
x1 y1 1
x2 y2 1
x3 y3 1 is zero
If the det=0, then the matrix is singular. Since the matrix is singular, the column vectors are lin. dep.

If a set of vectors are collinear, then the vectors are lin. dep.; hence, the det of the coefficient matrix is 0.