Answer:
Regular Pentagon
Step-by-step explanation:
A regular icosahedron is a twenty-faced polyhedron, each face being an equiangular triangle. Each vertex is joined together by 5 faces, therefore the polygon formed at each vertex is a regular pentagon.
We can also figure out the number of faces at each vertex using Euler's formula
F+V=E+2
F=number of faces = 20
E=number of edges = number of triangular faces * edges/triangle /2
(since each edge is shared between two faces)
= 20*3/2
=30
Number of vertices
= E+2-F = 30+2-20 = 12
So number of edges meeting at each vertex
= 30 / (12/2) = 30/6 = 5
(12/2 because each edge joins two vertices).
See attached figure, courtesy of Wikipedia.
1st answer: 2cm
2nd answer: 5m
3rd answer: 10dm
Answer:
B
Step-by-step explanation:
did the math
Put n=2 ,
f(2+1) = f(2) => f(3) = f(2) = 9
now, put n=1,
f(1+1) = f(1) => f(2) = f(1) = 9