# Stuck on example

Discussion in 'Electronics Homework Help' started by pump, Oct 12, 2012.

1. ### pump

24
0
Nov 4, 2011
Hi,
My lecture has given the following but I don't see where he has got 8.1 from....

2. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,505
2,852
Jan 21, 2010
Put those numbers in your calculator, execute the cosh^-1 function on them, and divide the result.

I get 8.0985163768965816846821597817253

Surely the question isn't this simple?

3. ### pump

24
0
Nov 4, 2011
Hi Steve,
Thank you for your reply. I can also enter the last equation into a calculator and get that result. However I couldn't see where he has got 57.05 from? Please see attached screenshot.

Thank you for taking the time to help me out here

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4. ### pump

24
0
Nov 4, 2011
Just looking again

I can only get the same answer as him if I subtract 512.8 in the top half of the equation?

5. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,505
2,852
Jan 21, 2010
You've missed a 1 and a closing parenthesis in your notes. you have "- )" where you should have written down "-1 )" then the closing parenthesis for the arccosh is missing.

Can you see where?

then substitute the numbers into it and the right answer comes out.

You realise what that 1/2 at the end is, right?

6. ### pump

24
0
Nov 4, 2011
The screenshots I have posted are from the lecturers notes which is why I am struggling to work the equation out. Just taking the top of the equation I get:

cosh-1 (2.863 x 397.107 x 0.5)
= cosh-1 (568.4586)

Where the lecture has got :
cosh-1 (57.05)

No I don't understand why the 1/2 is there either

7. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,505
2,852
Jan 21, 2010
The 1/2 is raising the value inside the brackets to the 1/2th power (square root)