Question 1141751
<pre>
Since the pentagon is a regular pentagon, all 5 of its sides are equal, so
each side is the perimeter divided by 5, and 15 mm divided by 5 is 3 mm.

In a right triangle with a hypotenuse of 5mm and a leg of 3mm, the other
leg is 

{{{a^2+b^2=c^2}}}
{{{a^2+3^2=5^2}}}

Solve that for a.

Since the triangle is a right triangle, we may consider one leg as the base
and the other leg as the height,

{{{A=expr(1/2)bh}}}

Substitute in that and solve for A

Edwin</pre>