What's the period of (cos ax)(sin bx)?

[sherifffruitfly]

For 0 < a, b < 1, if it makes a difference. Thanks!

[cp9876]

It is only periodic is a/b is rational and then it is fairly easy to work out.

Peter "Until the invention of the computer, the machine gun was the device that enabled humans to make the most mistakes in the smallest amount of time."

[MarkB777]

If you consider the wave form: y(t) = A*sin(w*t + q) A is the amplitude of the wave (height up the y axis) q is the phase shift of the wave (left/right shift along the x axis) t is a variable w is the angular frequency Angular frequency equals to 2*PI*f -> where f is the frequency of the wave. The period of the wave (t) is 1/f. (t = 1/f) A Cosine wave is just a Sine wave with a 90 degree phase shift. Cheers,

Mark Brock Click here to view my blog

[CPallini]

Since cos(ax) sin(bx) = 1/2 sin((a+b)x) + 1/2 cos((a-b)x) should be (a+b)/(a-b) rationale. :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
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