Question 368300
Let x = be the side of the equilateral triangle. Then by a direct use of the Pythagorean theorem, {{{5^2 + (x/2)^2 = x^2}}}.
{{{25 + x^2/4 = x^2}}},
{{{25 = 3x^2/4}}},
{{{x^2 = 100/3}}}, 
{{{x = 10/sqrt(3)}}} meters.