P is any point in the equilateral triangle ABC, PA = 3, Pb = 5, PC = 4, find the angle APC

P is any point in the equilateral triangle ABC, PA = 3, Pb = 5, PC = 4, find the angle APC

Taking point a as the axis, rotate the triangle ACP clockwise by 60 degrees. Point C coincides with point B, and point P arrives at point P1. AP1 = AP = 3, BP1 = CP = 4, angle p1ap = 60 degrees. Angle APC = angle ap1b connects p1p. We can know that triangle ap1p is an equilateral triangle. P1p = AP = 3. Angle ap1p = 60 degrees. BP1 = 4, BP = 5.3 ^ 2 + 4 ^ 2 = 5 ^ 2, so triangle BPI