最大值是1|A|=1A>0A=1图象经过点M(π/3,1/2)1/2=sin(π/3+φ)0<φ<ππ/3<φ+π/3<4π/3所以φ+π/3=5π/6φ=π/2f(x)=sin(x+π/2)=cosxf(a)=cosa=3/5f(b)=cosb=12/1300所以sina>0,sinb>0因为sin²x+cos²x=1所以sina=4/5,sinb=5/13f(a-b)=cos(a-b)=cosacosb+sinasinb=56/65
