 Hi and welcome to the session, let us discuss the following question, question says, evaluate cos 48 degrees minus sin 42 degrees. First of all let us understand that if theta is any acute angle in any right triangle then sin 90 minus theta is equal to cos theta. This is the key idea to solve the given question. Let us now start with the solution. We have to find cos 48 degrees minus sin 42 degrees. Now we know 48 degrees and 42 degrees are complementary angles. Now this 42 degrees can be written as 90 minus 48 degrees. So we can write this expression is equal to cos 48 degrees minus sin 90 minus 48 degrees. Now from key idea we know sin 90 minus theta is equal to cos theta. Here value of theta is 48 degrees. So sin 90 minus 48 degrees can be written as cos 48 degrees. So this is further equal to cos 48 degrees minus cos 48 degrees cos 48 degrees minus cos 48 degrees is equal to 0. So we get cos 48 degrees minus sin 42 degrees is equal to 0. 0 is our required answer. This completes the session. Hope you understood the solution. Take care and keep smiling.