Math Lecture

around 3 weeks ago i attended to lecture which was about the Math. the name of the lecturer was Barent Land, but im not sure about the name and around 30 students were in lecture. at the first the teacher said some rules about the lecture and he said "students should ask the question after the lecture and they cant use computer during the lecture. he started to teach student DEREVETIVE. it was really really hard and most of the students were confused. after that he gave us assignment and we did 1 of the question in the class. he used power point in during lecture. however, it was pretty easy to catch the lesson and some important details. during the lecture the professor was asked a lot of questions from students. also the atmosphere in the class was not relaxing becasuse the lecture and the teacher was reallt serious. unfortunetly i donno how can i explain the Derevetive becasue it was really hard and i didnt get most of the lecture.