sin(a+β)=33/65,cosβ=-5/13,a为锐角,β为钝角.求:sina

问题描述:

sin(a+β)=33/65,cosβ=-5/13,a为锐角,β为钝角.求:sina

sina=sin(a+b-b)
=sin(a+b)cosb-cos(a+b)sinb
=(33/65)*(-5/13)-(-56/65)(12/13)
=607/845