That equation is complicated. The four sides of the trapezoid are a, b , c and d.
height² = [(a +b -c +d) • (-a +b +c +d) • (a -b -c +d) • (a +b -c -d)] ÷ (4 • (a -c)²)
If you know the trapezoid area then you calculate:
height = (2 * trapezoid area) / (sum of the parallel sides)