The perimeter of an equilateral triangle is 45 centimeters. How do you find the length of an altitude of the triangle?
A triangle with 45 cm of perimeter has 15 cm of side. The
"altitude" connects the middle of one side to the opposite vertice. This forms a rectangle triangle with hypothenuse 15 cm and the small catet a= 7.5 cm. So by the Pythagoras theorem we must solve the equation:
Other solution was using trigonometry: