Решение
1 + cos(x + π/2) + cos(x - π/2) =
= 1 - sinx - sinx = 1 - 2sinx
при x = 5π/12
1 - 2sinx = 1 - 2sin(5π/12) = 1 - 2sin75° = 1 - 2 * 0,9659 = 1 - 1,9318 = - 0,9318
-1.8-1.5х=-3х+1.5-2
3х-1.5х= 1.8+1.5-2
1.5х=1.3
х=1.3/1.5
х=13/15
1){an}:9;9;9;9;9;...
2){an}:-3;0;5/3;3;21/5;...
3){an}:1;3/2;5/6;7/24;9/120;...
4) {an}:1/2;1/3; -1/8;1/13;-1/18;...
(вместо n подставляй поочередно 1,2,3,4,5 и вычисляй а1,а2 и т.д.)
= (а^1/2+в^1/3)^6 = а^(1/2*6)+в^(1/3*6) = а^3+в^2