Let us look at the image attached:
We can see that the height of the cone is 25.3 units and the diameter of the base is 10.4 units.
Now, the diameter of the base is 10.4 units so the radius of the base is given by

From the figure attached we can see that the height of the perpendicular in the triangle is 25.3 units and the length of the base is 5.2 units.
So, the angle made by the side of the cone with the base is given by




Therefore, the side of the cone makes
with the base of the cone.