Principal value of cos 1 root 3 2 July 8, 2019 16 32 64 128 Principal value of cos inverse root 3 by 2 cos inverse minus 1 by 2 Cos 1 cos 2 cos 3 Cosa=1 3 cos(a+b)=-1 3 求a b∈(0 p 2)求cos(a-b)
