sin61 ° =sin(90 ° -29 ° )=cos29 °
Тогда
sin29 ° *sin61 ° =sin29 ° *cos29 ° =
[blue]по формуле sin2 α =2sin α *cos α ⇒ sin α *cos α =(1/2)sin2 α [/blue]
=(1/2)sin(2*29 ° )=(1/2)sin58 °
[m]\frac{-6sin58^{o}}{sin29^{o}\cdot cos61^{o}}=\frac{-6sin58^{o}}{\frac{1}{2}sin58^{o}}=\frac{-6}{\frac{1}{2}}=-12[/m]
О т в е т. -12