Determine the length of the third side of the triangle that is hinged to the adjacent triangle. Due to the pyramid's square base, which composes the base of each triangle face, the length of the diagonal side is the square root of the length of the base of each triangle.

Compute the area of one of the faces of the triangle. All of the triangular faces in a pyramid should be of the same proportions. The area can be determined by using a simple formula: 1/2 of the (b) base times the (h) height.

Note that a perpendicular line down the center of one of the triangular faces creates two right triangles. Use the Pythagorean theorem later to determine the remaining angles of the triangle.

Use the formula 1= 2bh/squareroot(b^2+4h^2), with 1 being the value of the height of the line on the triangular face.

Use the formula squareroot(2)b to determine the length of the base of the triangular face. Because you must determine the length of a base line for one of the right triangles, divide this number in half. You now have two of the sides necessary (the hypotenuse and base) to complete the aforementioned Pythagorean theorem.

Substitute the values of the (h) height and (b) base into the formula: arcsin(squareroot(2) b/(2l)) = arcsin(sqrt(8h^2 + 2b^2)/4h). This will give you the angle of the pyramid from the apex to the base edge.