Need to know the surface area me figure out how to solve it

Sketch one cycle if the cosine function y=2cos2theta

How many quarts of a 50% solution of acid must be added to 20 quarts of a 20% solution of acid in order to get a 40% solution of acid?

Mr. roseanne will buy 12 1/2 pounds beef for for a cookout. the price for the first 3 pounds of beef is $4.99 per pound. after that, the price is $4.49 per pound. how much will mr. roshan pay for the beef