Question

I need help with number 4 of this problem? In part 3 every question is equal to 0.

http://wps.prenhall.com/wps/media/objects/1322/1354712/Ch6_PM%20Digital%20Trans.pdf

Here is the link

Answer 1

i don't think that every value for t in part 3 makes s(t) = 0

Answer 2

a. Sin(2pif(0))=sin(0)=0
b. Sin(2pif(1/4f))=sin(pi/2)=0
c. Sin(2pif(1/2f))=sin(pi)=0
d. Sin(2pif(3/4f)=sin(3pi)=0
e. Sin(2pif(1/f)=sin(2pi)=0
this is what i got...

Answer 3

sin(pi/2) = 0??? hmmm no, i don't think so haha

Answer 4

just for my own curiosity, what is \(f_0\) supposed to be?

Answer 5

oh whoops haha and i'm not really sure what it is

Answer 6

@satellite73 f is a variable for initial frequency, but it cancels so it is irrelevant

@Galleara sin(pi/2) = 1

Answer 7

@robz8 i did that one wrong lol thank you for correcting me :)

Answer 8

sin(3pi/2) = -1

Answer 9

if all your answers were 0, then your graph would be a horizontal line along the t-axis

Answer 10

but they're not, so your graph should look better now :)

Answer 11

right. so how do i enter those into a graph?

Answer 12

just like you would any normal graph

you order pairs will look like

(0, 0), (1/(4f), 1), (1/(2f), 0).... etc

Answer 13

you graph will end up looking like a wave going from 0 to 1 back down to 0 and back up to 1

Answer 14

oh ok thank you again!!

Answer 15

does it makes sense how to graph it? make your points in terms of f, because we don't know what the value of f is

Answer 16

in terms of f?

Answer 17

yeah, like have f included as part of your point

(0, 0), (1/(4f), 1), (1/(2f), 0)

Answer 18

like that!

Answer 19

sorry my curves are kinda sloppy

Answer 20

Except without the dc offset :-)

Answer 21

its ok and whats the dc offset?

Answer 22

direct current?

Answer 23

your sine wave is supposed to go 0 1 0 -1 0 1 0 -1 right?

the one just drawn doesn't go negative, it is 1/2 + 1/2 sin...

Answer 24

ahhh yeah :P my bad!

Answer 25

a dc offset is a constant factor added to the function....

Answer 26

so if i have to go for 12 cycles how do i do that??

Answer 27

Here's a graph showing the sine and the sine squished and offset for comparison

Answer 28

your 12 cycles would have points 0 1 0 -1 0 1 0 -1 (repeat that 6 times)