 Hi and welcome to the session. Let us discuss the following question. Question says, if tan 2a is equal to cot a minus 18 degrees, where 2a is an acute angle, find the value of a. First of all, let us understand that cot 90 minus theta is equal to tan theta, where theta is any acute angle in a right triangle. This is the key idea to solve the given question. Let us now start with the solution. We are given tan 2a is equal to cot a minus 18 degrees. Now we know 2a is an acute angle and we also know that tan theta is equal to cot 90 minus theta. Here value of theta is equal to 2a. So we can write tan 2a is equal to cot 90 degrees minus 2a. So we can write this implies cot 90 degrees minus 2a is equal to cot a minus 18 degrees. Now cot 90 degrees minus 2a is equal to cot a minus 18 degrees only when value of these two angles is equal. So this implies 90 degrees minus 2a is equal to a minus 18 degrees. Now adding 18 degrees on both the sides we get 108 degrees minus 2a is equal to a. Now adding 2a on both the sides we get 108 degrees is equal to 3a. Now dividing both the sides by 3 we get 36 degrees is equal to a or we can simply write it as a is equal to 36 degrees. So our required answer is angle a is equal to 36 degrees. This completes the session. Hope you understood the session. Take care. I'll have a nice day.