21 Trigonometric Identities Worksheet Concepts: • Trigonometric Identities - Reciprocal Identities - Pythagorean Identities - Periodicity Identities - Negative Angle Identitites (Sections 6.6 & 7.1) 1. Find the period, phase shift, and sketch the graph of y = 2 csc(2x − π2 ).