Question

The area of an isosceles triangle with sides $17cm,17cmand30cm$ is

• A.
  $289c{m}^2$
• B.
  $240c{m}^2$
• C.
  $60c{m}^2$
• D.
  $120c{m}^2$

Answer 1

The correct option is D

$120c{m}^2$

Area of an isosceles triangle $=\frac{b}{4}\sqrt{4a^2-b^2}=\frac{30}{4}\sqrt{4(17{)}^2-(30{)}^2}=\frac{15}{2}\sqrt{1156-900}=\frac{15}{2}\sqrt{256}=\frac{15}{2}\times 16=120c{m}^2$

So, option d is correct.