Question:
Each side of an equilateral triangle is 10 cm long. The height of the triangle is
(a) $10 \sqrt{3} \mathrm{~cm}$
(b) $5 \sqrt{3} \mathrm{~cm}$
(c) $10 \sqrt{2} \mathrm{~cm}$
(d) $5 \mathrm{~cm}$
Solution:
(b) $5 \sqrt{3} \mathrm{~cm}$
Height of equilateral triangle $=\frac{\sqrt{3}}{2} \times$ Side
$=\frac{\sqrt{3}}{2} \times 10$
$=5 \sqrt{3} \mathrm{~cm}$