Posted by **Katie** on Wednesday, March 23, 2011 at 6:09pm.

what is the length of any diagonal of a regular pentagon with a side of 20mm ?

- Geometry quick i have test tomorrow -
**Katie**, Wednesday, March 23, 2011 at 7:15pm
what is the length of any diagonal of a regular pentagon with a side of 20mm

- geometry -
**Reiny**, Wednesday, March 23, 2011 at 7:24pm
first find the size of each interior angle

angle = 180(5-2)/5 = 108°

let the length of the diagonal be x

by cosine law

x^2 = 20^2 + 20^2 -2(20)(20)cos 108°

I am sure you can finish it from there.

## Answer This Question

## Related Questions

- Geometry - what is the length of any diagonal of a regular pentagon with a side ...
- Geometry - A regular pentagon has side length 12cm.the perimeter of the pentagon...
- geometry - a regular pentagon has an apothem of 3.2 and an area of 37.2 cm. What...
- Geometry - Hi, I'm having a difficult time understanding a couple of Geometry ...
- Geometry - The perimeter of a regular pentagon is 31 cm. Find the length of each...
- Geometry - If a regular pentagon has sides of four feet, what is the length from...
- Geometry - If each side of a regular pentagon is x^2 + 17 and each side of a ...
- geometry - the lengths [in inches] of two sides of a regular pentagon are ...
- pentagon...GEOMETRY - ABCDE is a regular pentagon. FAD is an equilateral ...
- Geometry - What is the area of a regular pentagon with a side length of 9.4 feet...

More Related Questions