If msinA =ncosA then show that
tanA+cotA/tanA-cotA=nsinA + mcosA/nsinA-mcosA=n^2+m^2/n^2-m^2

Suppose that the price p (in dollars) and the weekly sales x (in thousands of units) of a certain commodity satisfy the demand equation 4p cubedplusx squaredequals38 comma 400. determine the rate at which sales are changing at a time when xequals80, pequals20, and the price is falling at the rate of $.20 per week.