The Fourier series of a real periodic function has only
- cosine terms if it is even
- sine terms if it is even
- cosine terms if it is odd
- sine terms if it is odd
Which of the above statements are correct?
- $\mathrm{P}$ and $\mathrm{S}$
- $\mathrm{P}$ and $\mathrm{R}$
- $\mathrm{Q}$ and $\mathrm{S}$
- $\mathrm{Q}$ and $\mathrm{R}$