Hello, students, today we are going to study very simple and interesting topic that is angles and triangles. First let us understand what is an angle and how do we name it. The definition states that an angle is formed by two rays having common origin. Two rays let us consider two rays. One and two, they have a common origin. Now, students do they have a common origin? Yes, so, my dear students, what can you say about this figure? It is an angle, superb.

Now, let us understand in more detail. The point which you can see is called as vertex of an angle. And these two rays are called as arms or sides of an angle. Now, let us understand, how do we name the angle? An angle can be named with the help of three alphabets or even a single alphabet also. First, let us understand using three alphabets. Example, ABC, how do we name the angle? Yes, you can write it as angle ABC or angle CBA. Whereas middle term is always a vertex of an angle, understood. Next, single alphabet, my dear students, single alphabet is always a vertex. So, as we discussed, which is the vertex. B, so, it is always a vertex and we can write it as, therefore ABC or CBA is also written as angle B. Very simple concept, very easy to understand. So, to get more clarification, let us solve exercise based on angles.

So, the very first exercise is, exercise 43, and sum number 1, now here we are supposed to find which of the following figures shows angles? Let us have first figure, yes. Now we have to identify whether it is an angle or not. Now, let us first quickly revise angle. What is an angle? It is having two rays. Second, the rays have a common origin. If both the conditions are satisfied, I can say this figure is an angle. Let us check first condition, having two rays. Do they have two rays? One, two, yes, it means our first condition is satisfied. Second, rays have a common origin. Let us check whether they have a common origin. Yes, again, it means our second condition is also satisfied. So, what can I say about this figure? Exactly it is an angle. Very simple sum, easy to understand. We will solve one more sum based on this.

Second figure, again we are given one figure and we are supposed to identify whether it is an angle or not? So, we will check first condition. Having two rays, do they have two rays? One, two, yes, it means our first condition is satisfied. Second they have a common origin, let us check whether they have a common origin or not. One, two, no, they don’t have a common origin. It means our second condition is not satisfied. Therefore, what can you say about the second figure. It is not an angle. Very simple sum, easy to understand.

Now, let us solve third sum based on this. Again we are given one figure. Now, it is very simple to identify, what we will do first? Identify, we will solve first condition. Having two rays, do they have two rays? One, two, yes, it means our first condition is satisfied. Second condition, they have a common origin. Do they have a common origin? Yes, again, it means our second condition is satisfied. So, what can you say about this figure. It is an angle. Very simple sums.