>>699,710
　(与式) = (1/2) -(3/2)/{5-4cos(x)}.
t=3tan(x/2) とおくと、cos(x)=(9-t^2)/(9+t^2),　dx=[6/(9+t^2)]dt,　(与式) = (1/2) -[(9+t^2)/6]/(1+t^2).
　∫(与式)dx = ∫{(1/2)-(3/2)/[5-4cos(x)] }dx = (1/2)∫dx - ∫ 1/(1+t^2) dt = x/2 - arctan(t) +c
　= x/2 - arctan(3tan(x/2)) +c.