The perimeter of a triangle whose two sides are 18 cm and 10 cm is 42 cm. Find the area of the triangle.
Answer & explanation
Correct answer: option 1
3rd side of triangle = 42 - 18 - 10 = 14
Semiperimeter of triangle (S) = \(\frac{42}{2}\) = 21
Area of triangle = \(\sqrt { S ( S - a) (S - b ) (S - c) }\)
= \(\sqrt { 21 × 7 × 11 ×3 }\)
= 21\(\sqrt { 11 }\)
The correct answer is Option (1) → $21\sqrt{11} cm^2$