Answer:
2√3 cm
Step-by-step explanation:
The side lengths of a 30°-60°-90° triangle have the ratio 1 : √3 : 2.
The altitude divides the triangle into two such 30-60-90 triangles, each with a short side that is half the length of the side of the equilateral triangle. The altitude is the long side of that 30-60-90 triangle, so is √3 times half of 4 cm:
... √3·(4 cm/2) = 2√3 cm
