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GATE 2024 BM – Question 30

Signals and Systems · Laplace and Fourier Transforms · 1 mark · Numerical answer

The periodic square wave shown has cosine/sine Fourier coefficients an,bn. Find a1/a3 to one decimal place.

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Correct answer: -3.0 to -3.0

Explanation

The waveform is even and alternates between plus and minus one with period four. For this even square wave, odd cosine coefficients are an=(4/(nπ))sin(nπ/2). Thus a1=4/π and a3=−4/(3π), yielding a1/a3=−3.0. Sine coefficients vanish by even symmetry.

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