Cos9x - cos5x = -2sin2x.sin7x
sin17x - sin3x = 2sin7x.cos10x
so f(x) =

=
#2 is answer 4, #3 is answer 3, #4 is answer 4. The answer to #5 is 6xy if it is a possibility.
Letter B or π is an irrational number, therefore it's the answer.
Answer:
d) 
Step-by-step explanation:
requires 
requires 
requires 
So, total amount of gasoline required for the trip is
.