i have a question for this problem

kwinrow · 2008-07-30 06:20:04

Consider two tones with frequencies of 220 and 223 Hz and pressures P1=.005sin440(pie)t and P2=.005sin446(pie)t, respectively. Graph the pressure P= P1+P2 felt by an eardrum over the 1-sec interval [.15,1.15]. How many beats are there in 1 sec?

my work:

am I goin about this right?

P=.005sin(440pit)+.005sin(446pit)
P=.01sin(886pit)

now is this ready to graph in the interval [.15,1.15]?

or is there another step i need to do?

ZHero · 2008-07-30 07:05:35

That's not right!
It should be..

now, you can use the formula

Last edited by ZHero (2008-07-30 07:15:05)

kwinrow · 2008-07-30 07:13:07

ok so its:

0.005[sin(440pit)+sin(446pit)]=2sin(440+446/2)cos(440-446/2)?

then after this i get all terms to one side right? then graph?

ZHero · 2008-07-30 07:22:34

You'll get..

now put the values of t in the range (0.15, 1.15) and find respective values of P and plot the graph accordingly...

Last edited by ZHero (2008-07-30 07:24:18)

kwinrow · 2008-07-30 07:58:12

so if i decide to plug in .44 as x i should get one single value right?

then using the order pair plot the dot?

John E. Franklin · 2008-07-30 09:29:45

ZHero wrote:

tiny typo correction:
423 should be 443 and 23 should be -3 because -6/2 is -3.
(sorry to be a pest)
(and don't forget the doubling or times 2 in that cool formula also)

P = 0.01 sin blah-blah cos blah-blah

Last edited by John E. Franklin (2008-07-30 09:32:48)

kwinrow · 2008-07-31 01:14:18

I have no idea how to finish this problem I am stuck on this step:

P=0.01(sin(443pit)cos(-3pit))

how do i finish this?when i graph it on the calculator i get nothing

John E. Franklin · 2008-07-31 04:10:19

Well, the -3 can also be +3 or just 3 due to the nature of the cosine.
And I don't have a graphing calculator, but try this instead and
make sure you are in radians, not degrees.

y = 0.01*sin(443*pi*x)*cos(3*pi*x)

If your calculator is in degrees, then replace the pi's with 180's like this:

y = 0.01*sin(443*180*x)*cos(3*180*x)

Also you won't be able to see the graph because it is too short,
you have to zoom in or make the equation 100 times taller like this:

y = 100*0.01*sin(443*180*x)*cos(3*180*x) (if in degrees use 180 for pi)

y = 100*0.01*sin(443*pi*x)*cos(3*pi*x) (if in radians, use pi)

kwinrow · 2008-07-31 08:43:15

thank you so much

Math Is Fun Forum

#1 2008-07-30 06:20:04

i have a question for this problem

#2 2008-07-30 07:05:35

Re: i have a question for this problem

#3 2008-07-30 07:13:07

Re: i have a question for this problem

#4 2008-07-30 07:22:34

Re: i have a question for this problem

#5 2008-07-30 07:58:12

Re: i have a question for this problem

#6 2008-07-30 09:29:45

Re: i have a question for this problem

#7 2008-07-31 01:14:18

Re: i have a question for this problem

#8 2008-07-31 04:10:19

Re: i have a question for this problem

#9 2008-07-31 08:43:15

Re: i have a question for this problem

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