In this trigonometry lesson, Julie Harland demonstrates how to verify a trig identity using basic identities and the identity for the cosine of a sum or difference. The problem is to prove that (cos(x+y))/(cosx * cosy) = 1 - tanx * tany. She shows two methods of proving the identity, one where you work on one side and simplify until it looks like the other side, and the other where you work on both sides. By the end of the lesson, you will have learned how to verify trig identities step-by-step.
We verify a Trig identity by using the basic identities and the identity for the cosine of a sum or difference. We prove that (cos(x+y))/(cosx * cosy) = 1 - tanx * tany using a trig proof.
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