1. =-2+7-4=1
2. = (-tgα)*ctgα+sin²α=-(1-sin²α)= -cos²α
233
1)5^9. 2)5^10
236
1)6^16:6^15=6^16-15=6^1=6
2)2^6-2^6=2^6-6=2^0=1
3)(7^14*7^6)/(7^18*7^2)=7^20/7^20=7^20-20=7^0=1
4)(5^5*5^5)/5^10=5^10/5^10=5^10-10=5^0=1
5)21^8/21^7=21^1=21
Sin(4x) - 1/2 = 0;
sin(4x) = 1/2;
4x=(-1)^k* pi/6 + pik;
x = (-1)^k* pi/24 + pik/4.
<em><u>Ответ:</u></em> 5ч. * 2мин.=10 минут