All About Area And Perimeter

Area Area is the measure of the actual surface of an object / figure. In two dimensional shapes, the area would be the space contained within the edges of the shape. We use the area of a 1cm x 1cm square which is called one square centimeter or 1cm². From rectangle ABCD, we can see that if we divide it in half from vertex to vertex, we form two right-angled triangles. A

B

vertex

height

C

base

D vertex

The height is equal to the length of the line segment with one endpoint at a vertex and the other endpoint on the line that contains the side opposite the vertex. Like all heights , this segment must be perpendicular to the line containing the side. The side opposite a given vertex is called the base of a triangle. Therefore the area of a right-angled triangle would be half the area of a rectangle. Area = ½ (l x b) Only that in triangles its length becomes its height. Therefore the correct formula is:

A = ½ (h x b) This formula for the area of a triangle applies to all types of triangles. In order to use this formula to calculate the area of a given triangle, its height and its base must be perpendicular( at right angles).

The base and perpendicular height of a triangle can be identified as follows:

Any side can be the base, and then the perpendicular height extends from the vertex opposite the base to meet the base at a 90° angle. For a right angled triangle, the perpendicular height can be one of the sides:

For an obtuse angled triangle (that is, a triangle with an angle greater than 90°) the perpendicular height may lie outside of the triangle itself: