galwaymathsgrinds.wordpress.com

Coordinate Geometry: Area of Triangle with Vertex at Origin

Area of blue triangle OPQ = area of red rectangle minus the area of the outer three triangles. = x2y1 – ½ [ (x1 y1 ) + (y2 -y1 )(x1 -x2 ) + (x2 y2 )] = x2y1 – ½ [ x1 y1 + x1 y2 – …