Since the measure of ∠K is 90º, we're dealing with a right triangle, where JI is the hypotenuse and KJ and IK the legs.
In a right triangle, the cosine of an angle is given by the ratio between the adjacent leg and the hypotenuse. The adjacent leg to ∠J is KJ and its measure is 20, the hypotenuse is JI and its measure is 29, therefore, their ratio is
[tex]\cos (J)=\frac{20}{29}=0.68965517241\ldots\approx0.69[/tex]And this is our answer.
