Answer
$73.18$ square units
Work Step by Step
The triangle being equilateral has all the three sides of equal length i.e. 13 unit each (given) and all angles of $60^{0}$ each.
(All angles of an equilateral triangle are equal and thus of $60^{0}$ each). Therefore-
Area, (A) of the triangle,
A = $ \frac{1}{2}$ a b $\sin \theta$
= $ \frac{1}{2} \times a\times a \times \sin \theta$
= $ \frac{1}{2} \times 13\times 13 \times \sin 60^{0}$
= $\frac{1}{2}\times169\times\frac{\sqrt 3}{2}$
=$\frac{169\sqrt 3}{4}$
= $73.18$ square units
