Trig Identities

Quotient Identities Reciprocal Identities OR OR OR Pythagorean Identities OR OR OR OR

Tips for proving trigonometric identities: You want to make the left and right hand sides of the identities match by substitution and cancellation. Work with the more complicated side of the identity. Begin by writing all expressions in terms of sine and/or cosine. If there is a squared term, check to see if you can use one of the Pythagorean identities. If so, use it to replace the squared term. You are finished when the left hand side of the identity EXACTLY matches the right side. You can not move a term from one side to the other side.

Handout Before we do some identities, lets practice substituting and cancelling. Write each expression as a single function or a constant. Hint: look at trig identities! Hint: change to sin and/or cos.

Handout Write each expression as a single function or a constant. Now we will try some with given ratios.

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Homework Handout #2-20 evens