split - decagon - Geometry Homework

[mathwhiz]

I need help finding the area of a decagon that has a perimeter of 220in. and a radius of 35.6. I don't know where to start. PLEASE HELP!!!!

 

[tkhunny]

Draw one apothem and ponder the meaning of right triangles.

By the way, it IS a REGULAR decagon, right?

 

[Deleted member 4993]

I need help finding the area of a decagon that has a perimeter of 220in. and a radius of 35.6. I don't know where to start. PLEASE HELP!!!!

alternatively,

Draw triangles with one vertex at the center and base as one of the sides of decagon.

If a triangle has sides a, b & c and

S = (a+b+c)/2

then

Area of the triangle = ?[S(S-a)(S-b)(S-c)]

This is known as Heron's formula.