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 top \ (C \). Each lateral rib of the pyramid is tilted to the plane of the base at an angle of 45 °. On the rib \ (s c \) point \ (F \) is the middle of this rib. Find the angle that forms a straight \ (a f \) with a plane \ (s a b \).