Find the First Six Terms of the Following Waveform

Essay

Find the first six terms of the following waveform. Assume half-wave symmetry.
$\begin{array}{|c|c|c|c|c|c|c|c|c|c|c|}\hline\boldsymbol{x}& 0^{\circ} & 20^{\circ} & 40^{\circ} & 60^{\circ} & 80^{\circ} & 100^{\circ} & 120^{\circ} & 140^{\circ} & 160^{\circ} &180^{\circ} \\\hline\boldsymbol{y} & 0 & 1.9 & 4.0 & 5.1 & 6.8 & 9.7 & 15.2 & 15.5 & 12.9 & 0 \\\hline\end{array}$