Usage of cotg; Area of polygon

Hi Forum

Here is a question

http://upload.wikimedia.org/wikipedi...Parameters.png

I am confused about the usage of cotg in this formula. How was this formula calculated?

If we use only tg we'd get

This angle regards the angle of the side , correct?

I'm no pro in co-trigonometric functions but,

Will this, in any way, relate to the fundamental propriety of cotg=A/O?

Trigonometric functions on non right angles are rather strange.

Thanks.

Re: Usage of cotg; Area of polygon

Re: Usage of cotg; Area of polygon

Quote:

Originally Posted by

**Plato** is the

*central angle* of a

**regular polygon**.

Thus we have

.

Note that

is the length of the altitude and

is the length of the base.

Hi Plato

I guess I didn't know how to put the central angle part in proper terms. Thanks for the explanation.

Though I'm kind of confused of where does the 2 in comes from.

Maybe we have a two there because is actually ?

Ok this was very confusing before your explanation.

I hope I got it right!

Thanks again Plato!