HALP MEH! This is So Confusing! What do I do?

What basic trigonometric identity would you use to verify that csc x sec x cot x = csc^(2)x

The blue whale is the largest animal living on the earth. the average blue whale measures 100 feet long (30 meters) and weighs 300,000 pounds (136,000 kilograms). a whale’s head is 1⁄3 of the length of its body. a new baby whale is 1⁄4 the length of a grown whale. the average man is 1⁄17 the length of a blue whale, and 1⁄1,818 its weight. a human baby measures 1⁄4 of the length of an adult. calculate the following information: how long is a whale’s head? how long is a new baby whale? how tall is the average man? how much does the average man weigh? how tall is the average human baby?

F(x)= 1/x-4, g(x)=4x+1/x a. use composition to prove whether or not the functions are inverses of each other. b. express the domain of the compositions using interval notation.