The base of a solid oblique pyramid is an equilateral triangle with a base edge length of 18 inches what is the height of the triangular base of the pyramid

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. 

Od. 130 degrees because if you add them together you get the 130