SOLUTION: Find the exact value of the expression cos(pi/12)cos(3pi/4) - sin(pi/12)sin(3pi/4) I appreciate your help!

Algebra ->  Algebra  -> Trigonometry-basics -> SOLUTION: Find the exact value of the expression cos(pi/12)cos(3pi/4) - sin(pi/12)sin(3pi/4) I appreciate your help!      Log On

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Question 140797: Find the exact value of the expression
cos(pi/12)cos(3pi/4) - sin(pi/12)sin(3pi/4)

I appreciate your help!
Answer by edjones(7311) About Me  (Show Source):
You can put this solution on YOUR website!
cos(pi/12)cos(3pi/4) - sin(pi/12)sin(3pi/4)
=((sqrt(3)/2)(-sqrt(2)/2))-((1/2)(sqrt(2)/2))
=-sqrt(6)/4 - sqrt(2)/4
=%28-sqrt%286%29-sqrt%282%29%29%2F4
=-.965926
.
Ed