Give each trig ratio as a fraction in simplest form​

One expression below in undefined, and the other expression has a well defined value. which expression is undefined and explain why it has no value. which expression is defined? what is the value of that expression and how do you know? what is a different expression using a trig inverse function that is also undefined?

Akayaker travels 3 miles upstream and 3 miles downstream in a total of 4 hours. in still water, the kayaker travels at a speed of 2 mph. what is the average speed of the river's current?

Alarge cheese pizza costs $18. each topping you add on costs $1.50. how much would it cost to get a large cheese pizza with cc toppings added? write your answer as an expression