Find the area of a triangle two sides of which are 18cm and 10cm and the perimeter is 42cm.
Solution
Two sides of the triangle = 18cm and 10cm
Perimeter of the triangle = 42cm
Third side of triangle = 42 - (18+10) cm = 14cm
Semi perimeter of triangle = 42/2 = 21cm
Using heron's formula,
Area of the triangle = √s (s-a) (s-b) (s-c)
= √21(21 - 18) (21 - 10) (21 - 14) cm2
= √21 × 3 × 11 × 7 m2
= 21√11 cm2
