Question

Simplify the following expressions.
a) cos(180º+x) + cos(180º-x)

b)cos(7π/126º)cos(36º/5)+sin(7π/126º)sin(36º/5)

Answer 1

cos(180+x) = -(cos(x))

cos(180-x) = -(cos(x))

I would take a gander and say that (a):

-2cos(x). but you should double check that. If I have learned anything in life, it is that I cannot be trusted :)