sina=5/13,a属于（π/2,π）,求sin(a+π/4),cos(a-π/6）,tan(a+π/3)
问题描述：
sina=5/13,a属于（π/2,π）,求sin(a+π/4),cos(a-π/6）,tan(a+π/3)
答
sin(a+π/4)=sinacosπ/4-cosasinπ/4=17√2/26
cos(a-π/6)=cosacosπ/6-sinasinπ/6
tan(a+π/3)=(tana+tanπ/3)/(1-tanatanπ/3)