Answers

2016-01-06T15:54:51+08:00
Using trigonometric identity,
cos^2(t) = (1/2)(cos(2t) + 1)
Since the Laplace transform of cos(at) is s/(s^2 + a^2) and the Laplace transform of 1 is 1/s, therefore
L{(1/2)(cos(2t) + 1)} = (1/2)L{cos(2t)} + (1/2)L{1}
= (1/2)[s/(s^2 + 2^2)] + (1/2)(1/s)
= (1/2)[s/(s^2 +4)] + 1/(2s)
= (s^2 + 2)/[s(s^2 + 4)]
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