Posted by **joy** on Monday, December 27, 2010 at 4:20pm.

im taking test

need answer quick'

use the sum and difference identities to write the expression as the cosine of the angle. be sure to simplify the anglee:

cospi/9cospi/3-sin

pi/9sinpi/3

- precal -
**Ms. Sue**, Monday, December 27, 2010 at 4:22pm
You're taking a test? Do you want us to help you cheat??

My, goodness, no!!

- precal -
**Reiny**, Monday, December 27, 2010 at 8:51pm
hint:

cos(A+B) = cosAcosB - sinAsinB

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