Question

If an isosceles triangle has a perimeter of 18 cm and base 8cm then it's area​

Answer 1

$\mathbb{MATHS \: SECTION} \\ \\ \sf \large \underline \red{Given:} \\ \\ \sf{ \implies \:Perimeter_{(isosceles \: triangle)} = 18cm} \\ \\ \sf{ \implies \: Base_{(isosceles \: triangle)} = 8cm} \\ \\ \\ \\ \sf \large \underline \green{To \: find:} \\ \\ \sf{ \implies \: Area_{(isosceles \: triangle)}} \\ \\ \sf \huge \underline \pink{Solution;} \\ \\ \sf \: let \: the \: side \: of \: isosceles \: triangle \: be \: a \: cm \\ \\ \sf \: acq \\ \\ \sf \: 2a + base \: = perimeter \: of \: isosceles \: triangle \\ \\ \sf \: 2a + 8 = 18 \\ \\ \sf \: 2a = 18 - 8 \\ \\ \sf \: 2 \times a = 10 \\ \\ \sf \: a = \frac{10}{2} \\ \\ \sf \: a = 5cm \\ \\ \sf{ \implies \: Area_{(isosceles \: triangle)}} = \frac{1}{2} \times base \times height \\ \\ = \sf \frac{1}{2} \times 8 \times 5 \\ \\ = \sf \: 4 \times 5 = 20 {cm}^{2}$