sin(a+b)=sinacosb+cosasinb=1/2
sin(a-b)=sinacosb-cosasinb=1/10 联立解得sinacosb=3/10 cosasinb=1/5
sinacosb/cosasinb=(sina/cosa)/(sinb/cosb)=3/2
sin(a+b)=sinacosb+cosasinb=1/2
sin(a-b)=sinacosb-cosasinb=1/10 联立解得sinacosb=3/10 cosasinb=1/5
sinacosb/cosasinb=(sina/cosa)/(sinb/cosb)=3/2