SOLUTION: A regular pentagon has sides of 20 cm. An inner pentagon with sides of 10 cm is inside and concentric to the large pentagon. determine the area inside and concentric to the larger

Algebra ->  Polygons -> SOLUTION: A regular pentagon has sides of 20 cm. An inner pentagon with sides of 10 cm is inside and concentric to the large pentagon. determine the area inside and concentric to the larger       Log On


   

Question 1178372: A regular pentagon has sides of 20 cm. An inner pentagon with sides of 10 cm is inside and concentric to the large pentagon. determine the area inside and concentric to the larger pentagon but outside of the smaller pentagon.
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!
For s+=+20:
A=%281%2F4%29sqrt%285%285%2B2sqrt%285%29%29%29%2As%5E2
A=%281%2F4%29sqrt%2847.3606797749979%29%2A20%5E2
A=%281%2F4%29%2A6.8819%2A400
A=6.8819%2A100
A=688.19cm%5E2


The area of the 10+cm :
A=%281%2F4%29sqrt%2847.3606797749979%29%2A10%5E2
A=%281%2F4%29%2A6.8819%2A100
A=6.8819%2A25
A=172.05cm%5E2


Area between : 688.19cm%5E2-172.05cm%5E2=516.14cm%5E2