 Hi and welcome to the session. Today we will learn some constructions related to angles. So first of all we will do construction of 60 degrees angle. For this first align segment AB of any length. So here we have align segment AB. Now use your compasses and with A as center and any radius which cuts segment AB at point P. So here we have a arc which cuts AB at point P. Now with same radius and P as center the previous arc at point Q. Here we have marked the point C. Thus AB is equal to 60 degrees. We will do the construction 30 degrees angle. That half of 60 degrees will be equal to 30 degrees. We have already constructed angle CAB equal to 60 degrees in our previous construction. So if we bisect this angle that is angle CAB which is equal to 60 degrees. Then each of the angle will be equal to 30 degrees. So to construct 30 degrees angle we will bisect the angle 60 degrees. So let us construct the bisector of angle CAB and we have already learnt how to draw the bisector of an angle construction. We have angle CAB and we have an arc which cuts line segment AB at point P. Now open your compasses more than half of PQ. Then with P and Q as center draw two arcs to cut each other at point R. So here we have two arcs. Now join AR to get the bisector of angle CAB. Thus here angle CAR and angle RAB both are equal to 30 degrees. This is how we construct an angle of 30 degrees. Next we will do the construction of 120 degrees angle. So for this our first step is draw a line segment AB of any length like this with A as center in radius in segment AB at point P. As a third step with same radius center previous arc again and Q as center at the same arc. So we got the point R lastly join AR. So we have joined AR and we have marked this point as thus angle CAB is equal to 120 degrees. Now as our last construction we will do the construction 90 degrees angle. Line AB is perpendicular to the line BC then between these two lines will be 90 degrees. So if we want to construct an angle of 90 degrees at a line then on that point we will draw the perpendicular then we will get the angle of 90 degrees. We have already learnt how to construct the perpendicular at a point on the line. To construct of 90 degrees we will construct the perpendicular to a line, line on the line. So let's see how to construct the angle of 90 degrees. Here we have a line segment AB and we need to construct an angle of 90 degrees at point A. First of all we will extend the line segment BA. Let us name it as so we have a line segment XB. Now with AS center in any radius we will draw an arc to cut the line segment XB at points P and Q. Now open your eyes more than PAB as center draw two arcs to cut each other at point R. Now we will join the points AR at this point as C thus angle CAB is equal to 90 degrees. So by constructing the perpendicular at point A we have constructed the angle CAB equal to 90 degrees. So in this session we have learnt the construction of 60 degree angle, construction of 30 degrees angle, construction of 120 degrees angle and finally construction of 90 degrees angle. With this we finish this session. Hope you must have understood all the constructions. Goodbye take care and have a nice day.