SOLUTION: using sum, difference, half, or double angle formulas and the exact value chart in the solution, find the exact value of cos 105 degrees.

SOLUTION: using sum, difference, half, or double angle formulas and the exact value chart in the solution, find the exact value of cos 105 degrees.

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Question 34006: using sum, difference, half, or double angle formulas and the exact value chart in the solution, find the exact value of cos 105 degrees.
Answer by venugopalramana(3286) (Show Source): You can put this solution on YOUR website!
COS(105)=COS(60+45)=COS 60 * COS 45 - SIN 60 * SIN 45
=(1/2)*(1/SQRT2)-(SQRT3/2)*(1/SQRT2)
=(1-SQRT3)/2SQRT2=-0.25882
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