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Absolute Value Problem (1 Viewer)

frenzal_dude

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I need to find the absolute value of b(t):



Here is the answer in the textbook:


However I got a different answer when working it out, and can't understand how they got to that result from the textbook.
Here is my working out:











 

AAEldar

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I need to find the absolute value of b(t):



Here is the answer in the textbook:


However I got a different answer when working it out, and can't understand how they got to that result from the textbook.
Here is my working out:











Fixed it up so far... Not seeing where the is coming from though... Will look at it more.

All I can think of is that it has something to do with there being a square root of the , so when doing that you divide through by 2 and it goes.
 
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AAEldar

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Because and





That's still different though...
 

D94

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Are you sure there's no equal sign or an OR written between ?

After endless working out, I resulted in Wolfram Alpha, and it said the two above are equal to each other, so did you read the answer correctly?

If what I'm saying is right, then look at AAEldar's working because that's correct.
 

AAEldar

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do you reckon it's an error in the textbook?
Hard to say. This is from a Uni text book correct? I could be missing something, but from what I've done I can't see anywhere else to go.

D94 raises a good point too.
 

frenzal_dude

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Are you sure there's no equal sign or an OR written between ?

After endless working out, I resulted in Wolfram Alpha, and it said the two above are equal to each other, so did you read the answer correctly?

If what I'm saying is right, then look at AAEldar's working because that's correct.
It has to be an error in the textbook, another reason to think this is because they even forgot to put the end bracket for the 2(1+cos(.....

Thanks for your help, I went through your working out and it seems fine, they obviously forgot to put "=a(t)" before the "2|cos(PItT)|"
 

AAEldar

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It has to be an error in the textbook, another reason to think this is because they even forgot to put the end bracket for the 2(1+cos(.....

Thanks for your help, I went through your working out and it seems fine, they obviously forgot to put "=a(t)" before the "2|cos(PItT)|"
Didn't even notice that! Haha. Sounds like you're right though.
 

zhiying

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Woah saw this in the MX2 section and nearly had a heart attack, why do this to me night before exam T_T
 

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