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May 23, 2015

Homework Help: Trigonometry

Posted by Timothy on Monday, March 17, 2008 at 6:26pm.

Hello, everyone:

I am working on finding the exact values of angles that are less common and are therefor not found easily on the Unit Circle (at least, they are not labeled). For example, the problem I am asking about is:

10) Find the exact values of the Sine, Cosine and Tangent of 255. We are supposed to use common angles to assist in our answers (for example, 255 = 300-45), and use formulas provided to solve them. I can get sine and cosine alright, but the tangent equation is causing a massive migraine:

tan(x-y) = (tan(x)-tan(y))/(1+tan(x)tan(y))

Using the formula, I get this result:

tan(300-45)=(tan(300)-tan(45))/(1+tan(300)tan(45))

Here is where I am stuck. Problem is, I did not understand the example in the notes, and the book's examples have virtually nothing to do with the actual exercise problems. So, I am trying to deduce this by logic. The denominator appears to be a conjugate, so I tried multiplying by (1-tan(300)tan(45)), and got this result:

[tan(300)+tan^2(300)tan(45)-tan(45)-tan(300)tan^2(45)]/(1-tan^2(300)tan^2(45))

Besides being nightmarishly complex, it also appears to be a dead end. I would appreciate it, greatly, if someone could take their time and slowly explain how to do this portion of my assignment?

With kind regards (except for my math teacher),

Timothy

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