Polar Co-ordinates

area of triangle ABC∠AOB = 170 degree - 80 degree = 90 degreearea of triangle OAB = 1/2 (11)(12) sin90 degree = 66 ∠BOC = 250 degree - 170 degree = 80 degree area of triangle BOC = 1/2(12)(13) sin 80 degree = 76.815 ∠AOC = 250 degree - 80 degree = 170degree area of triangle AOC = 1/2 (11)(13) sin 170degree = 12.4158 hence area of triangle ABC.= area of △ OAB + area of △ BOC - area of △AOC = 66 + 76.815 - 12.4158= 130.3992= 130 units^2(3 s.f.)