A question about a combination of signals ?

Original post by john.ashby

so i have 3 formulas and i think i can plot 2 of them
but i need to combine the two to make a new 3rd one

not quite sure how to do this, any tips ?

[4 + 2 cos (2pi 10 x 10^3t) cos (2Pi 125 10^3t)]

would you leave out the t element as this is the X axis scale ?

Are you simply trying to plot them or ... what is the original question?

Reply 2

OP

the original question is, here are 2 wave forms in formula, and i have to show these on a graph, which i think i have done,
Vc = 4cos (2 pi 125 x 10^3t) 125khz
Va = 2cos(2 pi 10 x 10^3t) 10khz
then the questions says the you need to plot the 2 outputs multipled together to create a new Vo output
maybe i am not seeing how to multiple the two together to create a smaller equation to plot

sorry for the bad notation, is there an easy way to insert correct maths formulas on this forum ?

Reply 3

Original post by john.ashby

the original question is, here are 2 wave forms in formula, and i have to show these on a graph, which i think i have done,
Vc = 4cos (2 pi 125 x 10^3t) 125khz
Va = 2cos(2 pi 10 x 10^3t) 10khz
then the questions says the you need to plot the 2 outputs multipled together to create a new Vo output
maybe i am not seeing how to multiple the two together to create a smaller equation to plot

sorry for the bad notation, is there an easy way to insert correct maths formulas on this forum ?

If youre using desmos to plot, simply do soemthing like
y = 4*cos(t)*2*cos(3*t)

For maths you can use the [noparse]

[/noparse]
tags and write latex between them. So

[br]V_c = 4 \cos (2 \pi 125 \times 10^3 t) [br]

(edited 1 year ago)

Reply 4

DFranklin

18

Original post by mqb2766

There should be no spaces in tags - Ive just put them in to make them render.

In case you didn't know: TSR has a [noparse][noparse]
tag that you can put around stuff you don't want it to interpret.

Reply 5

[quote="DFranklin;98284432"]In case you didn't know: TSR has a
[noparse][noparse]
tag that you can put around stuff you don't want it to interpret.[/noparse]
Thanks - I didnt, but will edit it now.

Reply 6

OP

i have this so far in desmos, but i can seem to get the scale correct so you can actually see whats going on between the 3 wavs
https://www.desmos.com/calculator/wwfekfhcfr

Reply 7

Original post by john.ashby

i have this so far in desmos, but i can seem to get the scale correct so you can actually see whats going on between the 3 wavs
https://www.desmos.com/calculator/wwfekfhcfr

The signals should be like
cos (2*Pi*(125*10^3)*t)
with extra brackets and operators to make it clear? Time is a multiplier, not an exponent. 125*10^3 represents the frequency of the signal as usual, so its 2*pi*frequency*time

(edited 1 year ago)

Reply 8

OP

Original post by mqb2766

The signals should be like
cos (2*Pi*(125*10^3)*t)
with extra brackets and operators to make it clear? Time is a multiplier, not an exponent. 125*10^3 represents the frequency of the signal as usual, so its 2*pi*frequency*time

so does this attempt look correct ? https://www.desmos.com/calculator/upxjlnnwbm

Reply 9

Original post by john.ashby

so does this attempt look correct ? https://www.desmos.com/calculator/upxjlnnwbm

Looks about right for the first 4. Im not sure how v0 is defined, so cant say whether its/theyre correct or not.

Reply 10

OP

i need to plot this one also, but not sure how to achieve it in desmos, i know to change the t for x
4cos (2pi 125 x 10^3t) + cos (2pi135 x 10^3t) + cos (2pi115 x 10^3t)

Reply 11

Original post by john.ashby

i need to plot this one also, but not sure how to achieve it in desmos, i know to change the t for x
4cos (2pi 125 x 10^3t) + cos (2pi135 x 10^3t) + cos (2pi115 x 10^3t)

Pretty much just type it in so
y = 4*cos(...) + cos(...) + cos(...)
similar to your other signals

Reply 12

OP