In ΔFGH, f = 3.1 inches, g = 2 inches and h=3.2 inches. Find the measure of ∠F to the nearest 10th of a degree.
Using the Law of Cosines
3.1^2 = 2^2 + 3.2^2 - 2 (2)(3.2) cos F
[ 3.1^2 - 2^2 - 3.2^2 ] / [- 2 * 2 * 3.2 ] = cos F
Using the cosine inverse
arccos ( [ 3.1^2 - 2^2 - 3.2^2 ] / [- 2 * 2 * 3.2 ] ) = F ≈ 68.8°
