(cos a + cos b)^2 + (sin a + sin b)^2=?

First, we expand the equation:



Then, we combine certain terms in order to simplify them using trigonometry identities.



Note these identities:
Pythagoran relation: 
Sum and Difference Formula/Identities: 

Thus, if we apply these identities, the simplified equation would be:


Simplying further, the answer would be

D) the x-intercept represents adam's commission pay when he had zero total sales