Difficult math problem: triangle ABC, angle c = 90 degrees, angle a = 30 degrees, triangle C point does not move, rotates counterclockwise, edge AC intersects AB at f point, Triangle ABC, angle c = 90 degrees, angle a = 30 degrees, triangle C point does not move, rotates counter clockwise, edge AC (CD side after rotation) intersects AB at f point, triangle after rotation is CDE. Rotation angle is ﹤ 0 ﹤ 0 ﹤ 0 ﹤ 0 ﹤ 0 ﹤ 0 ﹤ 0 ﹤ 0 ﹤ 0&

Difficult math problem: triangle ABC, angle c = 90 degrees, angle a = 30 degrees, triangle C point does not move, rotates counterclockwise, edge AC intersects AB at f point, Triangle ABC, angle c = 90 degrees, angle a = 30 degrees, triangle C point does not move, rotates counter clockwise, edge AC (CD side after rotation) intersects AB at f point, triangle after rotation is CDE. Rotation angle is ﹤ 0 ﹤ 0 ﹤ 0 ﹤ 0 ﹤ 0 ﹤ 0 ﹤ 0 ﹤ 0 ﹤ 0&

If AFD is an isosceles triangle and ad = DF, then DAF = & + 30, because AC = CD, then ADC = & + 30, so 2 (& + 30) + & + 30 + 30 = 180, then & = 20
Similarly, if ad = AF, then & = 40 degrees