Answer:
Option D. [tex]cos(54\°)=\frac{0.5s}{7}[/tex]
Step-by-step explanation:
we know that
A regular pentagon can be divided into 5 isosceles triangles
The length side of the legs of one isosceles triangle is equal to the radius
The vertex angle of one isosceles triangle is equal to 360/5=72 degrees
The base angle of one isosceles triangle is equal to 54 degrees
Let
s------> the length side of the regular pentagon
so
[tex]cos(54\°)=\frac{(s/2)}{r}[/tex]
substitute the given value
[tex]cos(54\°)=\frac{(s/2)}{7}[/tex]
[tex]cos(54\°)=\frac{0.5s}{7}[/tex]
