The perimeter of a right triangle is 40 cm and its hypotenuse measures 17 cm. Find the area of the triangle.
Given: Perimeter = 40 cm
Hypotenuse = 17 cm
The diagram is given as:
Let the sides be a, b and c(hypotenuse).
Therefore, a + b + c = 40 cm
⇒ a + b + 17 = 40 cm
⇒ a + b = 40 - 17 cm
⇒ a + b = 23 cm
⇒ a = (23-b) cm
Now we know that,
Base2 + Perpendicular2 = Hypotenuse2
⇒ a2 + b2 = c2
⇒ (23-b)2 + b2 = 172
⇒ 232 + b2-46b + b2 = 289
⇒ 529 + b2-46b + b2 = 289
⇒ 2b2-46b + 240 = 0
⇒ b2-23b + 120 = 0
⇒ b2-8b-15b + 120 = 0
⇒ b(b-8)-15(b-8) = 0
⇒ (b-8)(b-15) = 0
This gives us two equations,
i. b-8 = 0
⇒ b = 8
ii. b-15 = 0
⇒ b = 15
Let b = 8 cm
⇒ a = (23-b) cm
⇒ a = (23-8) cm
⇒ a = 15 cm
Now,
Area of triangle = 1/2 × base × height
= 1/2 × 8 × 15
= 60 cm2