tg(arcos(-1/4)+pi/2))=sin(y)/cos(y),

 где у= arcos(-1/4)+pi/2

sin(y)=сos(-arcos(-1/4))=-0,25

сos(y)=+ sqrt(1- sin^2(y))=sqrt((1-0 ,25)*(1+0,25))=0 ,25*sqrt(15)

tg(arcos(-1/4)+pi/2))=-1 /sqrt(15)=-sqrt(15)/15