= Solution
For explicit sketches take a symmetric, 50% <duty cycle> square wave with levels $\pm V_0$. The source does not specify levels or duty cycle; a unipolar 50% wave follows by adding its mean and rescaling. Let $\tau=RC$ and $M$ be the positive output extremum in the periodic steady state. The <square-wave response of an RC low-pass filter> has
$$
M=V_0\tanh\frac{T}{4\tau},\qquad
V_{\mathrm{out}}(t)=\begin{cases}
V_0-(V_0+M)e^{-t/\tau},&0\leq t<T/2,\\
-V_0+(V_0+M)e^{-(t-T/2)/\tau},&T/2\leq t<T,
\end{cases}
$$
extended periodically. The extremum formula follows by imposing $V_{\mathrm{out}}(0)=-M$ and $V_{\mathrm{out}}(T/2)=M$. It makes the three regimes below quantitative, including their finite amplitudes.
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