Attempt the question, check the explanation, and continue with similar questions to build confidence before exams.
sin(x + y) = sin(x) + sin(y)
sin(x + y) = sin(x)cos(y) + cos(x)sin(y)
sin(x + y) = sin(x)sin(y)
sin(x + y) = cos(x)cos(y) - sin(x)sin(y)
Continue with nearby questions to strengthen the same chapter concept while you still have the context fresh in mind.