Plotting sin wave help

Hi all,

I'm looking for some help with a question around plotting of sin wave of a graph as part of my HNC in Electrical Engineering. Judging by searching on the forum at previous posts this has been a typical problem posted on here but can't quite find a resolution. Any help would be much appreciated.

The question is:

One of your commonly used laboratory instantaneous test signal voltages (vs) is described by the equation… Vs = 8sin(2p*pie*f*t - pie/4) where f = 500 kHz and t, represents time.

Make the time t, the subject of this formula, and hence determine the first point in time when the instantaneous signal voltage has a magnitude of +5V.

Note: A colleague has reminded you that you need to have your calculator in radians mode (RAD) for this calculation, because the angle is given in radians (i.e. π is featured).

Use this software or this software to draw at least two cycles of this signal and annotate the drawing so that your non-technical colleagues may understand the relevant information it contains.

I have (or at least I think I have) managed to get t on it's own and come up with 4.7 x 10-7 as the value for t.

I have began plotting this here: https://www.desmos.com/calculator/aezwx6kvuu

Which looks... ok? My issue is I cannot verify against my formula or previous workings whether the graph looks correct.

I would have also expected the x axis be in the order of magnitude small enough for me to see t as 4.6 x 10^7, however my x axis is just a count.

I feel like I'm close, but not quite getting it conceptually well enough to verify or understand what I'm doing wrong.

Any guidance would be much appreciate, thank you in advance and apologies for the long post!

Reply 1

mqb2766

Original post by AdamMc90

Hi all,
I'm looking for some help with a question around plotting of sin wave of a graph as part of my HNC in Electrical Engineering. Judging by searching on the forum at previous posts this has been a typical problem posted on here but can't quite find a resolution. Any help would be much appreciated.
The question is:
One of your commonly used laboratory instantaneous test signal voltages (vs) is described by the equation… Vs = 8sin(2p*pie*f*t - pie/4) where f = 500 kHz and t, represents time.
Make the time t, the subject of this formula, and hence determine the first point in time when the instantaneous signal voltage has a magnitude of +5V.
Note: A colleague has reminded you that you need to have your calculator in radians mode (RAD) for this calculation, because the angle is given in radians (i.e. π is featured).
Use this software or this software to draw at least two cycles of this signal and annotate the drawing so that your non-technical colleagues may understand the relevant information it contains.
I have (or at least I think I have) managed to get t on it's own and come up with 4.7 x 10-7 as the value for t.
I have began plotting this here: https://www.desmos.com/calculator/aezwx6kvuu
Which looks... ok? My issue is I cannot verify against my formula or previous workings whether the graph looks correct.
I would have also expected the x axis be in the order of magnitude small enough for me to see t as 4.6 x 10^7, however my x axis is just a count.
I feel like I'm close, but not quite getting it conceptually well enough to verify or understand what I'm doing wrong.
Any guidance would be much appreciate, thank you in advance and apologies for the long post!

The time you quote, 4.7 x 10-7, must correspond to a voltage (5v) and by the sounds of it they want you to plot
vs = 8sin(2*pi*f*t - pi/4)
where t is the independent variable (x) and vs is the dependent variable (y). You plot exactly that function (dont substitute a value for t and then introduce another independent variable), then draw the horizontal/vertical lines corresponding to
vs = 5
t = 4.7 x 10-7
and they must cross at a point on the curve which corresponds to what you want to find.