 So, in this session, we are going to discuss another fundamental relation between the trigonometric ratios. In the last session, we observed that sin square theta, this was our, this is what we learned in the last session, sin square theta plus cos square theta is always 1 irrespective of whatever is the value of theta, it is always 1. Now, this we did by dividing this equation which we obtained using Pythagoras theorem by h square last time. Now, this time, let us divide it by p square. So, last time we divided by h square. Now, we can divide this time by p square. So, dividing, dividing 1 by p squared, p squared. So, what will you get? You will get h squared upon p squared is equal to p squared upon p squared plus b squared upon p squared. So, you know, we can divide an equation by some non-zero quantity. So, p is perpendicular length here in the triangle ABC. So, hence, it is division by p square is allowed. Now, what? Let us closely look at this triangle and try to find out what is h upon p. So, if you see look, if you closely look at it, h upon p is nothing but hypotenuse by opposite. Isn't it? What is hypotenuse upon opposite? It is nothing but cosecant theta. Okay, it is nothing but 1 upon sin theta, isn't it? Now, similarly, b upon p is nothing but adjacent, adjacent divided by opposite, which is nothing but cotangent theta or cot theta. Okay? So, hence, what do we learn? We learn here that h upon p square can be written as h by p whole square is equal to 1 by p square by p square is 1 plus plus. So, h square h by p whole square is equal to 1 upon b by p whole square, isn't it? So, what did we find out? h by p is nothing but cosecant theta. So, cosecant theta whole squared is equal to 1 plus cotangent theta cot theta whole square, correct? Which can now be written as cosecant square theta is equal to 1 plus cot square theta, isn't it? So, this is another very, very important relationship. It is going to be used a lot in trigonometry. Now, so, there can be many, many other forms as we discussed in the last session as well. So, you can write cosecant square theta minus cot square theta is equal to 1. This is also another way of writing it. Another way of writing it would be cosecant square theta minus 1 is equal to cot square theta, isn't it? So, whichever format is required, you can use this. And then this can be further reduced as cosecant theta minus cot theta. This is times cosecant theta plus cot theta is equal to 1. How? Because if you see, this thing is in the form of a square minus b square, isn't it? So, a square minus b square is a minus b a plus b, isn't it? So, using that, I have written this particular relation. Similarly, this can be simplified as cosecant theta. So, I am factoring it. cosecant theta minus 1 times cosecant theta cosecant theta plus 1 is equal to cot square theta. So, these are multiple ways of writing the same relation.