# trig identies 5.3 &5.4

use a sum or difference identity to find an exact value

pie/12

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1. cos pie/12

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2. Hmmm. 15 degrees. I know 45, and 30, so why not the difference?

Cos15=cos(45-30) = you know the formula

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bobpursley
3. i got it nevermind

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