Divide the polygon into 5 triangles by using each side as a base and joining the vertices of the polygon to a common point (for example, the centre). If the polygon is regular the angle at the vertex of each triangle is 360/5=72 degrees, so you have 5 isosceles triangles of equal area. Find the area of one and multiply by 5 to get the total area.multiply 5 times the lenght of oneside
