Co-ordinate Geometry

Co-ordinate Geometry

1. Distance Formula

   • AB = Root of ([x2-x1]^2 + [y2-y1]^2)
   • Used in determining if or what quad the fig is
   • A(x1, y1)
   • B(x2, y2)
   • Also used to find if line is collinear or not

2. Section Formula

   • Let point P divide AB in the ratio m:n
   • P(x,y); A(x1,y1); B(x2,y2)
   • x = (mx2+nx1)/(m+n)
   • y = (my2+ny1)/(m+n)

3. Area of triangle

   • A(x1,y1); B(x2,y2); C(x3,y3)
   • 1/2 * [x1(y2-y3) + x2(y1-y3) + x3(y2-y1)]
   • Collinearlility: x1(y2-y3) + x2(y1-y3) + x3(y2-y1) = 0