 and welcome to the session I am Deepika here. Let's discuss the question if angle A and angle B are acute angles such that cos A is equal to cos B then show that angle A is equal to angle B. Now we know that according to the Pythagoras theorem in right angle A, B, C, A C square is equal to A B square plus B C square that is hypotenuse square is equal to sum of this case of other two sides and cos theta is equal to side adjacent to angle theta that is B C upon hypotenuse A C. So this is a key idea behind our question of this key idea to solve our question. So let's start the solution given cos A is equal to cos B so therefore A is equal to P upon A C is equal to Q B upon R B is equal to Q B upon I assume this is equal to K let us take this as number 1 plus B C square and R B square is equal to B Q square plus Q R square therefore C is equal to root of A C square minus P A square is equal to R B square Q B square Q B square. So by using this push through to the sides of other triangles, triangles are equal to triangles are single. So therefore triangle P A C is similar to triangle Q B R and hence angle is equal to angle B. So this only we have to prove. So I hope the question is clear to you by and taken.