The height of the triangular base of the pyramid is calculated through the equation, h = (cos x)(18 in) where h is height and x is half of the angle of the triangle. Since the triangle is equilateral, the value of x is 30°. Substituting, h = (cos 30°)(18 in) h = 15.59 in Thus, the height of the base is approximately 15.59 inches.
