Trig Proof 6
In this lesson, Julie Harland teaches us how to verify a trig identity using basic identities and the identity for the cosine of a sum or difference. She takes us step-by-step through the process of proving that (cos(x+y))/(cos(x - y) = (coty - tanx)/(coty + tanx) by simplifying one side at a time and changing cotangents and tangents into sines and cosines. She also demonstrates how to multiply the numerator and denominator by the least common denominator to get rid of a complex fraction. By the end of the lesson, we learn how to do a formal proof or a more informal proof, both of which are valid.
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))/(cos(x - y) = (coty - tanx)/(coty + tanx) using a trig proof.
More free YouTube videos by Julie Harland are organized at http://yourmathgal.com
- How do you prove trig identities?
- How do you verify a trig identity using the basic identities and the identity for the cosine of a difference or sum?
- How do you prove that (cos(x+y))/(cos(x - y) = (coty - tanx)/(coty + tanx) using a trig proof?
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Staff Review
This lesson shows how to prove another trig identity by solving one side of the equal sign to look like the other side. This is a great tutorial video for proving a trig identity. All steps are shown and explained.
