we know that surface area=2*[area of the base]+perimeter of the base*height find the area of the base
is an equilateral triangle b=15/3----> 5 in applying the law of sines to find the area Area=(1/2)*b²*sin 60°------> area=(1/2)*5²*sin 60°----> 10.8253 in²
alternative method to find the area of the equilateral triangle find the h value applying the Pythagoras theorem h²=5²-2.5²-----> h=√18.75-----> h=4.33 in area=b*h/2----> area=5*4.33/2----> 10.8253 in²
