5.3.2.30 Various problems in the space

Condition: At the base of the pyramid \( S A B C \) lies an isosceles triangle with a right angle at the vertex \( C \). Each side edge of the pyramid is inclined to the plane of the base at an angle of 45°. On the edge \( S C \) the point \( F \) is the midpoint of this edge. Find the angle formed by the straight line \( A F \) with the plane \( S A B \).