tg(5n/4+arccos(-3/4))=(tg(5n/4)+tg(arccos(-3/4)))/(1-tg(5/4)*tg(arccos(-3/4)))=(1+tg(arccos(-3/4)))/(1-tg(arccos(-3/4)))
tg(arccos(-3/4))=sin(arccos(-3/4))/cos(arccos(-3/4))=sqrt(1-cos^2(arccos(-3/4)))/(-3/4)=sqrt(1-9/16)/(-3/4)=(5/4)/(-3/4)=-5/3
tg(5n/4+arccos(-3/4))=(tg(5n/4)+tg(arccos(-3/4)))/(1-tg(5/4)*tg(arccos(-3/4)))=(1+tg(arccos(-3/4)))/(1-tg(arccos(-3/4)))
tg(arccos(-3/4))=sin(arccos(-3/4))/cos(arccos(-3/4))=sqrt(1-cos^2(arccos(-3/4)))/(-3/4)=sqrt(1-9/16)/(-3/4)=(5/4)/(-3/4)=-5/3