 Hi and welcome to the session. Today we will learn about polygons. A polygon is a simple leader of line segments. For example, this is a polygon. Now the line segments in a polygon are called av, vc, cd, de and ea are the sides of this polygon. Also with a common end point av and ae have a common endpoint a. That means these are adjacent sides. Sites va and vc have a common end point b. So these are also adjacent sides and so on. Next we have the meeting point, the side av and ae meet at a point a. So a is a vertex. Also point v, cd and e are other vertices of the given polygon. Also the end points of a polygon, the adjacent of side av, that is point a and b are adjacent vertices. Similarly v and c, c and d, d and e and e and a are other pairs of adjacent vertices. Now points a and c are not adjacent, points v and d are not adjacent and so on. So the joint adjacent, so here ac, ad, ve, vd and ce are the diagonals of the polygon. Now let's move on to our next topic, angles is made up of from a common. For example here we have two rays starting from a common end point say o. Now let's name these rays as op and oq. It is formed by the rays op and oq. Here o is the vertex and we denote this angle by angle p, o, q. Then specifying the angle the vertex that is o is always written as the middle letter. So here we have the common is the vertex and oq are the arms or sides of the angle p, o, q of a region. The shaded region is the interior of the angle. So we can say that the point y lies in the interior of the angle. The remaining area that is this one is the exterior of the, we can say that the point z lies in the exterior of the angle. The interior and the exterior restricted areas, they can extend indefinitely since the two sides can extend indefinitely. Now let's move on to our next topic, triangles and ce. Interior of triangle abc. So we can say the interior of triangle abc is ab, bc and ce are the c. That means the point z lies on the triangle abc, which the vertices are named, that is d. So this is a quadrilateral abc, t, av, line segment bc, cd and line segment da. Angle b and angle c are adjacent, angle c are adjacent angles.