Please check Misc 8 of Chapter 5 Class 12 here https://www.teachoo.com/3726/706/Misc-8---Differentiate-cos-(a-cos-x---b-sin-x)---CBSE/category/Miscellaneous/
Teachoo is free. Login to view more pages.
Login with facebook
Login with gmail
On signing up you are confirming that you have read and agree to
Terms of Service