设圆半径为r,圆心为O依题可得∠AOB=∠BOC=∠COD∠DOE=∠EOF=∠FOA∠AOB+∠BOC+∠COD+∠DOE+∠EOF+∠FOA=360°∠AOB+∠FOA=120°,cos∠AOB=（2r²-1）/2r²,sin∠AOB=根号（1/r²-1/4r的四次）cos∠FOA=...