HPC Section 5.4 Sum and Difference Formulas Pt 1

True or False:

$$\cos\ \left(30\ +\ 45\right)\ =\ \cos\ \left(30\right)\ +\ \cos\ \left(45\right)$$  

True or False:

$$\cos\ \left(x\ +\ 2\right)\ =\ \cos\ \left(x\right)\ +\ \cos\ \left(2\right)$$  

You know the answer to this:  Think about the graph. 

What does this represent?
$$y\ =\cos\ \left(x\ +\ 2\right)\$$  

You know the answer to this:  Think about the graph. 

What does this represent? (in radians)
$$y\ =\ \cos\ \left(x\right)\ +\ \cos\ \left(2\right)$$  

Simplify and solve:
$$\cdot\cos78\degree\cos18\degree+\sin78\degree\sin18\degree=$$