cos180°= -1

ctg270°= 0

sin360°= 0

tg²60°= 0

3×(-1)+5×0-0-3= -6

[tex]\displaystyle\bf\\3Cos180^\circ+5Ctg270^\circ-2Sin360^\circ-tg^{2} 60^\circ=\\\\\\=3\cdot (-1)+5\cdot 0-2\cdot 0-(\sqrt{3} )^{2} =-3+0-0-3=-6[/tex]