Find the area of the triangle with sides 8.6 cm, 9.1cm and 9.7cm. First find the size of one of the angles.
Use the law of cosines.
cosA = (-a^2+b^2+c^2)/2bc.
cosA=(-(8.6)^2+(9.1)^2+(9.7)^2)/176.54 =
0.58310.
A = 54.33o.
Area = 0.5*bc*sinA.
Area=0.5*9.1*9.7*sin(54.33) = 35.9 cm^2