Giving the right triangle jkl what is the value of cos (l)

For the right triangle to be given in name of three letters such as this, the right angle is most likely to be in the center, in this case letter K. To determine the common trigonometric properties of a certain angle we may use of the mnemonics SOH - CAH - TOA. 

                         sin angle = opposite side / hypotenuse

                         cosine angle = adjacent side / hypotenuse

                         tangent angle = opposite side / adjacent side

If we let small letter j, k, and l be the sides opposite to angles J, K, and L, respectively. Then, the cos (L) will be,

                                      cos (L) = j/k

81 is a composite number.