Answer:
11.55
Step-by-step explanation:
An equilateral triangle is one which all it sides are equal.
10cm altitude means the height is 10cm.
Using Pythagoras theorem,
x² = 10² + (x/2)²
Assume that the side of the triangle is xcm
x² - x²/4 = 100
3x²/4 = 100
x = √(400/3)
x = 11.55cm
