| Abstract: | This paper deal with the existence of periodic solutions of the nonlinear cscillation equation
$$\\mathop x\limits^{ \cdot \cdot } + f(x)\varphi (x) + \psi (x)\eta (x) = 0\begin{array}{*{20}{c}}
{}&{(3)}
\end{array}\]$$
The author offers a method which can reduce (3) into system
$$\\mathop x\limits^ \cdot = h(y) - e(y)F(x),\mathop y\limits^ \cdot = - g(x)\begin{array}{*{20}{c}}
{}&{(9)}
\end{array}\]$$
Some sufficient condition for the existence of the limit cycles of (9) are obtained. These results generalize the results in 1,2,3,4,5,6]. |
