(adsbygoogle = window.adsbygoogle || []).push({}); [SOLVED] Unit Circle

How can I use the unit circle to get the right answer. I understand the 30 60 90 and 45 45 90 triangles, but come to a problem when using this method with cosine. For example cosine(3pi/2) is -[2^(1/2)]/2. Using my method I get the positive. Please explain the methods of using the unit circle.

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# Homework Help: Unit Circle

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