A REGULAR PENTAGON AND A SQUARE ABFG ARE FORMED ON OPPOSITE SIDE OF AB FIND ANGLE BCF.

Answer 1

In triangle BCF, sides BC and BF are equal, since they are both the length s of one side of the pentagon.

angle B is 18° (90°-72°, the exterior angle of the pentagon)

So, since BCF is isosceles, angle BCF = (180-18)/2 = 81°