All sides of an equilateral triangle are equal, so all three sides are 9 cm. To find h, use the pythagorean theorem. This requires use of only one right triangle, where we use b as our h.
a^2+b^2=c^2 (4.5)^2+b^2=(9)^2 (20.25)+b^2=(81) b^2=(81/20.25) or 4 square root both sides b=2
