Well, keep in mind that all geometric figures have a derived area formula that are generally universal. As a result, by separating the irregular shape into multiple geometric shapes, all you have to do is add their respective areas through their respective formulas. For example, take the shape of an ice cream cone with a semi circular scoop of ice cream. We could clearly see that the geometric shape of a cone and a semi circle is involved. Therefore, we use the area of a cone, A=pi(r)(r+(rad)h^2+r^2), plus the area of a semi circle, 4pi(r^2).