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Mathematics 21 Online
OpenStudy (anonymous):

Use the cosine sum and difference identities to find the exact value. COS(5pi/6)

OpenStudy (aravindg):

Here is a hint cos(5pi/6)=cos(pi-pi/6)

OpenStudy (anonymous):

that's what i thought but i thought you couldn't use 180 and 90 degrees

OpenStudy (anonymous):

lol

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