In ΔJKL, j = 93 cm, k = 82 cm and l=86 cm. Find the measure of ∠J to the nearest degree.

Use cos rule

 

93^2 = 82^2 +86^2 - 2 (82)(86) cos J      solve for J

(93^2 - 82^2 -86^2)/ ((-2)(86)(82)] = Cos J    

J =~ 67^o