Use an Addition or Subtraction Formula to find the exact value of the expression, as demonstrated in Example 1.
cos
(41π/
12)
cos (41 pi / 12)
Convert radians to degrees = ( 41pi / 12 ) * 180 /pi - (41/12)*180 = 615°
615 - 360 = 255°
cos (255°) = cos (210 + 45) =
cos 210 cos 45 - sin 210 sin 45 =
(- √3/2 ) ( √2/ 2) - (- 1/2)( √2/2) =
- √6/4 + √2/4 =
√2 - √6
________
4
+318 
