X² + x - 10 = x - 1 это система
x - 1 >0
x² - 9 = 0
x > 1
x = 3 или x = - 3
x > 1
x = 3
Cos альфа = - 1/9
sin^2 alfa = 1 - cos^2 alfa
sin^2 alfa = 1 -1/81=80/81
1+tg^2alfa=1/cos^2alfa
1+tg^2alfa=1/1/81
1+tg^2alfa=81
tg^2alfa=80
1+ctg^2 alfa=1/sin^2alfa
1+ctg^2alfa=1/80/81
1+ctg^2alfa=81/80
ctg^2alfa=1/80
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