how to constuct an equilateral triangle given its altitude is 4 cm?

 

Steps for construction an equilateral triangle, when altitude  is given :

(1) Draw a line MN

(2) Make a point D on line MN. At D draw an altitude DR.

(3) Cut off DA = 4 cm from DR.

(4) Draw angle DAC = 30 degree, which meets MM at point C.

(5) Mark a point B on MN such that AC = CB

(6) join AB

Hence Triangle ABC is an equilateral triangle.