Find the fundamental periods of the following signals: (a) x1 (t)=10cos(5πt) (b) xn2 (t)=10cos(5πt)+2sin(7πt) (c) x3 (t)=10cos(5πt)+2sin(7πt)+3cos(6.5πt) (d) x4 (t)=exp(j6πt) (e) x5 (t)=exp(j6πt)+exp(−j6πt) (f) x6(t)=exp(j6πt)+exp(j7πt)