How would you write this equation in terms of sin and cos as well as simplify it from there? (1+cotx)(1-cotx)-csc^2 x

Kilgore trout creates a new scale to diagnose depression. however, his scale only assesses one symptom of depression while ignoring others. which of the following is his new scale most likely lacking? a) test-retest reliability b) discriminant validity c) criterion validity d) alternate-forms reliability e) content validity f) none of the above