Sin/Cos derivative question


#1

On page 5 of the textbook (this is the link to the textbook https://s3.amazonaws.com/saylordotorg-resources/wwwresources/site/wp-content/uploads/2012/12/MA005-3.2-Definition-of-Derivative.pdf) it says that"we calculated the second and fourth limits in section 1.2". Where in section 1.2 is it? I can’t seem to figure out how to do it.