Tga / ctga + 1 = tga / (1/tga) +1 = (tga)^2 +1
1 ; - 1 ; 2/3 ; - 15 ; 0,(8) ; - 1/2
(-2sin(68-22)/2)*(sin(68+22)/2)/(2sin(68-22)/2)*(cos(68+22)/2) = -sin45 /cos45 = -tg45 = -1
Х^7 × ( х³ )^6 = х^25.
х^3 × 6 = х^18;
х^7 + 18 = х^25.
(an):
an=0,5n-3;
a1=0,5-3=-2,5;
a2=1-3=-2;
a3=1,5-3=-1,5;
...
a30=15-3=12;
d=0,5;
SUM=a1+a2+a3+...+a30;
SUM=30a1+435d;
SUM= 30 * -2,5 + 435 * 0,5;
SUM=-75 + 435/2;
SUM= 217,5-75;
SUM=142,5
Ответ: 142,5