In this lesson, Math Gal demonstrates how to verify a tricky trig identity using basic identities and the identity for the cosine of a sum or difference. By manipulating the left-hand side of the equation using these methods, Math Gal is able to transform it into the right-hand side of the equation, ultimately proving that (cos(A + B))/(sin(A - B)) = (1 - tanA * tanB)/(tanA - tanB). This lesson is a great resource for anyone struggling with trig identities and looking to improve their problem solving skills in this area.
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(A + B))/(sin(A - B)) = (1 - tanA * tanB)/(tanA - tanB) using a trig proof.
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