The fundamental period of a composite signal can be found by LCM(individual time periods of the components of signal)...

If I have a cubed signal like sin^3(2t)

using this concept I use trigonometric identity (sin^3(X) = (3/4)sinX - (1/4)sin(3X) ) to convert the signal into summation and then apply the same rule of LCM .

(3/4) sin(2t)-(1/4)(sin(6t))

T1=2pi/2 = pi

T2= 2pi/6 = pi/3

LCM(pi,pi/3) = pi

T= pi sec

But the answer to this question is (1/pi) sec...

How can we find the fundamental period of this signal ??

(This question is from the book signals and systems by Simon Haykin(page#22, Pb 1.5(b)))