8. cos333/2sin63=cos(270+63)/2sin63=sin63/2sin63=1/2
9. 9tg67/ctg23=9tg(90-23)/ctg23=9ctg23/ctg23=9
10. 3tg42*tg312=3tg42*tg(270+42)=-3tg42*ctg42=-3
11. 5sin570=5sin(360+210)=5sin210=5sin(180+30)=-sin30=-0.5
12. 7√2cos225=7√2cos(180+45)= - 7√2cos45= -7√2*√2/2= - 7
13. 6tg11π/4=6tg(3π-π/4)=6tg(-π/4)= -6*1=-6
14. 8√3sin11π/3=8√3sin(4π-π/3)=-8√3sinπ/3=-8√3*√3/2=-4*3=-12