2) cos²a+ctg²a+ sin²a=1+ ctg²a = 1+ctg²π/6=1+(√3)²=1+3=4
1/cos²a-1= (1-cos²a)/cos²a= sin²a/cos²a= tg²a = tg²π/3= √3²=3
3) sin(-90°)+cos(-90°)+sin²(-45°)= -1+0+(√2/2)²=1+1/2=1,5
6sin(-30°)-2cos(-60°)+tg²60° = 6*(-1/2)-2*1/2+√3²=-3-1+3=-1
10ctg(-135°)*sin(-225°)*cos(-315°) = 10*1*(√2/2)*(√2/2)=10*1/2=5