Answer:
20√3 cm
Step-by-step explanation:
Altitude of an equilateral triangle splits it into 2 equal right triangles, it bisects the base and the angle opposite to the base.
Let the altitude be x. Then as per Pythagorean theorem:
- x² = 40² - (40/2)²
- x²= 1600 -400
- x²= 1200
- x= √1200
- x= 20√3 cm
Correct choice is the second one
