If cos a 4 5 cos b 12 13 July 8, 2019 16 32 64 128 If sin a 4 5 and cos b 12 13 Cosa=1 3 cos(a+b)=-1 3 求a b∈(0 p 2)求cos(a-b) If 0 a b π/4 and sin(a+b)=24/25 and cos(a-b)=4/5 then find the value of tan2a