Ответ:

Пошаговое объяснение:

1)sin48°cos12°+cos48sin12=sin(48+12)=

=sin60°=кор3/3

(cos15+sin15)^2=cos^2 15+sin^2 15 +

+2sin15cos15=1+2sin30=1+1=2

cos^2t-cos2t=cos^2t-2cos^2t+1=

=1-cos^2t=sin^2t

sin140/2cos70=2sin70cos70/2cos70=

=sin70°

sin28+sin16=2sin22cos6°

cosn/15-cosn/30=cos12°-cos6°=

=-2sin9°sin3°

4) cos^2x=1-sin^2x=1-9/25=16/25

cosx=4/5 siny=- 4/5

sin(x+y)=sinxcosy+cosxsiny=

=3/5(-3/5)+4/5(-4/5)=-9/25-16/26= -1