Posted by Christine on Sunday, June 6, 2010 at 9:49pm.
Find the exact value by using an appropriate sum or difference identity.
- Algebra 2 Honors - Reiny, Sunday, June 6, 2010 at 9:54pm
For these type of questions, you must split up your given angles into a sum or a difference of angles whose trig ratios you know
e.g. 165 = 120+45
= cos120cos45 - sin120sin45
you should know both sin45 and cos45
sin120 = sin60
cos120 = -cos60
take it from here
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