 Hi and welcome to the session. I am Asha and I am going to help you with the following question which says, prove the following and we have to prove that cot x into cot 2x minus cot 2x into cot 3x minus cot 3x into cot x is equal to 1. So, first let us learn identity 12 of your book which is cot of a plus b is equal to cot a into cot b minus 1 upon cot a plus cot p and by using this identity we can write cot x plus 2x is equal to cot x into cot 2x into cot 2x minus 1 upon cot x plus cot 2x and cot x plus 2x is nothing but cot 3x. So, with the help of this idea we are going to prove the above problem. So, this is our key idea. Let us now start with the solution and the left hand side of the problem is cot x into cot 2x minus cot 2x into cot 3x minus cot 3x into cot x. Now, taking cot 3x common it can further be written as cot x into cot 2x minus cot 3x in the bracket we have cot 2x plus cot x which is further equal to cot x into cot 2x and cot 3x with the help of key idea can be written as cot x into cot 2x minus 1 upon cot x plus cot 2x here we have cot 2x plus cot x. Now, this is common. So, we will cancel it and we have cot x into cot 2x minus on opening the bracket we have cot x into cot 2x plus 1 again these two are opposite signs. So, I am canceling we are left with 1 which is the right hand side of the equation. Hence, we have left hand side is equal to right hand side and that is proved. So, this completes the solution. Hope you enjoyed it. Take care and have a good day.