Cos 4 5 cos 12 13 July 8, 2019 16 32 64 128 Cos a 4 5 cos b 12 13 Cos inverse 4 5 cos inverse 12 13 tan inverse 56 33 Prove that cos 4 5 cos 12 13 cos 33 65 If cos x 4 5 cos y 12 13 If cos theta 4 5 and cos phi 12 13 Cos 1 cos 2 cos 3 Cosa=1 3 cos(a+b)=-1 3 求a b∈(0 p 2)求cos(a-b)
