Alan

As shown the internal angle is 160, so the external angle is 20. If there are n trapezoids then: 

20n = 360

so n = 18

There are an infinite number of solutions to the question as written!  

The four corners are triangles each of side 2.9 cm and diagonal sqrt(2)*2.9 cm

They can be put together to make two squares each of area 2.9^2 cm^2, so the area of the octagon is the area of the original  square less the area of the 4 triangles, namely:

Area = 10^2 - 2*2.9^2 cm^2

Perimeter = 4*sqrt(2)*2.9 + 4*(10 - 2*2.9) cm

I'll leave you to do the number crunching.

You'll need to specify the current, A, if you want a numerical answer!

If you mean in polar form then:

a +b.i = r.e^(i.A)  where r = sqrt(a^2 + b^2)  and A = arctan(b/a)

I just used a piece of numerical software.  I also thought it was a brain teaser at first and looked for a simpler way; however, I couldn't see one! 

Now if the individual terms were squared instead of square-rooted, it would be a different matter.

As follows:

-1+2^1/2-3^1/2+4^1/2-5^1/2............+2014^1/2 ≈ 22.061

You can't square each individual term Solveit.  If x = -1+2^1/2-3^1/2+4^1/2-5^1/2............+2014^1/2

it is not true that x^2 = -1 + 2 -3 + 4 -5 +...-2013 + 2014

Did you use tinypic upload?  http://tinypic.com/?t=postupload

Choose file.

Upload now  (you might have to click on the spam protection box and enter a key phrase - this isn't always required).

Then copy the url in the 4th box down; the one labelled Direct Link for Layouts

Back in the forum answer editor select the Image icon and paste the url into URL upload box then click on OK.

Here's my attempt (basically the same as heureka's):

I tried to upload this from my phone yesterday (I was away from my computer), but with no success!