If P (-5, -3), Q (-4, -6) , R (2, -3) and S (1, 2) are the vertices of a quadrilateral PQRS, find its area.
Area of triangle is given by 12|x1(y2−y3)+x2(y3−y1)+x3(y1−y2)|
Area of quadrilateral PQRS = Area of triangle PQR + Area of triangle PSR
=12|−5(−6+3)−4(−3+3)+2(−3+6)|+12|−5(2+3)+1(−3+3)+2(−3−2)|
=10.5+17.5=28 sq. units