Докажите, пожалуйста (формально): sin (α + π) = – sin α , cos (α + π) = – cos α ,
Answers & Comments
Zhiraffe
Sin (α + π) = sin α*cos π + sin π * cos α = – 1*sin α + 0* cos α = - sin α cos (α + π) = cos α*cos π - sin π * sin α = –1* cos α -0*sin α = –cos α
Answers & Comments
cos (α + π) = cos α*cos π - sin π * sin α = –1* cos α -0*sin α = –cos α