Answer
$43.3$ square units
Work Step by Step
The triangle being equilateral has all the three sides of equal length i.e. 10 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 10\times 10 \times \sin 60^{0}$
= $\frac{1}{2}\times100\times\frac{\sqrt 3}{2}$
=$\frac{50\sqrt 3}{2}$ = $25\times1.732$
= $43.3$ square units