First we are going to find the common denominator of both fractions. To do that, we are going to multiply their denominators:

Now we can rewrite our expression using the common denominator:

Finally, we can use the trig identities:

and

to simplify our trig expression:
We can conclude that the correct answer is the fourth one.
Answer:
We call the denominator rational.
Step-by-step explanation:
For example:

It's clear that the denominator is now a rational number, not an irrational one anymore.
30000L is larger than 3kL
Just split it in half and get 91,000 and put it on each side of the bar graph. 91,000 plus 91,000 equels 182,000