Assume the maximum value of the sine wave is 1.2V (two diode potentials using the constant-voltage model of a silicon diode). Match the slope of the triangle wave vtri (q) to that of the sine wave vs(q) at q = 0; this allows you to compute the maximal value Vtri of the triangle wave. Thenmatch the slope of the sine wave to that of the triangle wave multiplied by Rb /(Ra + Rb) when the triangle wave voltage reaches Vtri/2. This allows you to compute the ratio of the resistors.
Assume that the points of inflection of the piecewise-linear transfer characteristic occur at 29° (vs(q) = 0.6V) and 73° (vs(q) = 1.2V). Use the first point of inflection to determine the maximal value Vtri of the triangle wave and use the change in vs relative to the change in vtri between 29° and 73° to calculate the ratio of the resistors.