You can find a unit rate by dividing the first number by another number to get something per something. For example, if a question asked: What is the unit rare for 100 feet for 2 seconds, it would be 100/2, so it is 50 feet per second.
The given expression is the expansion of cos (a-b)
so we can simply calculate it as <span>cos(112-45)= cos 67</span>
I tried to solve this and I got the answer B
