4 replies to this topic

[deepmadan]

A point moves along a sine wave..
its positions or values are y1, y2 and y3 at times 0, t2 and t3 respectively.

find the amplitude, frequency and initial phase of the sine wave..

y1 = amp * sin(phase)
y2 = amp * sin(w*t2 + phase)
y3 = amp * sin(w*t3 + phase)

please reply me the possible solution to this such that the result has minimal error...

[WingedPanther]

Are you looking for the algorithm to solve this? If so, you're in trouble. You need a minimum of four data points to solve for the information you want, and depending on the data points you may not be able tell anyway.

[deepmadan]

ya i need an algorithm or any hint how to proceed..

if the frequency is also known then is it possible to find a suitable algorithm to find amp and phase.. if yes ??? how ??

thanks..

[WingedPanther]

w=1/frequency.

sin(w*t+phase) = sin(w*t)cos(phase)+sin(phase)cos(w*t)
sin(phase) = cos(pi/2 - phase)

Combined gives us:
y1 = amp * sin(phase)
y2 = amp * sin(w*t2 + phase) = amp*sin(w*t2)cos(phase) + y1 cos(w*t2)
y3 = amp * sin(w*t3 + phase) = amp*sin(w*t3)cos(phase) + y1 cos(w*t3)

Playing around with some real values should get you closer.

[deepmadan]

i have played around with values and got some results quite closer to the answers...

but didnt got any accurate resultss..

so need some other algorithms to get more accurate results..

thankss..