A whole class discussion in Calculus 3 about the classification of maxima, minima and saddle points.
The students were given the equation for D but had to find out themselves how to use this equation
to classify a critical point. All groups wrote several examples on the wrap around blackboards to use
as classification examples.
The class had 25 students and met two times a week for 75 minutes each and one time for 50 minutes.