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Step-by-step explanation:

Right Triangles

Right triangles are those who have a right angle, i.e. 90°. The other two angles must sum 90° to complete the 180° which must sum the internal angles of a triangle.

The image shows a circle with two similar triangles FAD and EAD. We know they are congruent because they share the same height and have a base of the same value (as indicated by the ticks). The segment AD must be perpendicular to FE since it comes from the center of the circle. We can conclude is right, i.e. measures 90°.

We know , so the required angle must be 90°-48°=42°.

I hope it help and I guess it is correct