8704:17=512=8^3
5831:17=343=7^3
3672:17=216=6^3
2125:17=125=5^3
1088:17=64=4^3
Tg'x+ctg'x=1/cos²x-1/sin²x
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Cos(2*7x) + sin(7x) = 1
1 - 2sin^2(7x) + sin(7x) = 1
sin(7x)*(1 - 2sin(7x)) = 0
1) sin(7x) = 0
7x = πk
x = πk/7
2) sin(7x) = 1/2
7x = π/6 + 2πk, x = π/42 + 2πk/7
7x = 5π/6 + 2πk, x = 5π/42 + 2πk/7