# sinusoidal function

• Jun 8th 2012, 02:43 PM
gordonmckee
sinusoidal function
need help with this can you provide any light on it.....

The instantaneous value of current, i amp, at t seconds is given by

i= 15 sin (100 pi t + 0.6)

Find
the amplitude
the period
the frequency
the initial phase angle when t =0 expressed in both radians and degrees
the value of i when t=2.5
the time in milliseconds when the current first reaches its maximum value

I need all the help I can get thanks
• Jun 8th 2012, 04:36 PM
pickslides
Re: sinusoidal function
For $\displaystyle y = A \sin B (x-C)$

A is the amplitude and $\displaystyle \frac{2\pi}{B}$ is the period, can you answer the first two now?
• Jun 8th 2012, 10:00 PM
gordonmckee
Re: sinusoidal function
no sorry can you help some more
• Jun 9th 2012, 02:23 PM
skeeter
Re: sinusoidal function
Quote:

Originally Posted by gordonmckee
no sorry can you help some more

you really need to research how sinusoidal graphs are transformed ...

http://youtu.be/CuvO9-Zk2Xc
• Jun 10th 2012, 11:42 AM
gordonmckee
Re: sinusoidal function
Amplitude ---- 15

Period ---- 2 pi / 100 pi = 1/50

Frequency ---- F=1 / (1/50) = 50Hz

Phase Angle ---- 0.6 rad = (0.6 x (180/pi)) = 34.38deg or 34o 23' leading

I ----15 sin (100 pi 2.5 + 0.6) = 15 sin (786) = 15 x 0.9063 = 13.59Amps

Time ---- 15 = 15 sin (100 pi t + 0.6)

arcsin 15 / 15 = ( 100 pi t + 0.6)

100 pi t = 1.5708 - 0.6

t = 0.9708 / 100 pi

t = 0.0031

= 3.1 ms

• Jun 11th 2012, 12:25 PM
gordonmckee
Re: sinusoidal function
can anyone varify if i'm right on this or not
Thanks
• Jun 12th 2012, 09:59 AM
gordonmckee
Re: sinusoidal function
I take it I am on the right track with this then.....
• Jun 14th 2012, 12:41 PM
gordonmckee
Re: sinusoidal function