делал так:
y = x + arctg y
х - у + arctg y = 0
1 - y' + 1/(1+y^2) * y' = 0
1 = y' - 1/(1 + y^2) * y'
1 = y' * (1 - 1/(1 + y^2))
1 = y' * y^2/(1 + y^2)
y' = (1 + y^2)/y^2
y' = 1 + 1/y^2
А дальше
y'' = (1 + 1/y^2)' = -2 * 1/y^3 * y' = -2 * 1/y^3 * (1 + 1/y^2) = -2/y^3 * (y^2 + 1)/y^2 =
= -2 * (y^2 + 1)/y^5
Правильно?
Да, правильно.
Русская версия Invision Power Board (http://www.invisionboard.com)
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