Consider the following analogue signal s(t): s(t)=20 \cos (10 \pi t)+20 \cos ^{2}(10 \pi t) Where time t is expressed in seconds. Analyse this signal by answering the following questions:

a) Use Fourier transform to find the frequency spectrum S(f) of s(t). You may directly use the common Fourier Transforms listed at the end of Chapter 3.(1,5 Marks) b) Using 5Hz/cm as horizontal scale, represent S(f) graphically on cartesian axes.