$1.$ Given the periodic signal $\backslash ($ v$($t$)\backslash )$ shown below:

a$.$ Determine the trigonometric Fourier series representation for $\backslash ($ v$($t$)\backslash ).$

b$.$ Write the first four terms of the Fourier series representation of $\backslash ($ v$($t$)\backslash )$ in the magnitude$-$phase form.

c$.$ Using the results from part a or b$,$ write the first three terms of the Fourier series representation of $\backslash ($ v$($t$)\backslash )$ in exponential form.