Rectange \(JKLM\) is shown below. The given side lengths are in feet. What is the cosine of \(\angle{KJL}\) ?

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Cosine refers to the ratio of the adjacent side to the hypotenuse. We can obtain the hypotenuse through the pythagorean theorem:

$$ a^2+b^2=c^2$$ $$ 9^2+7^2 = c^2 $$ $$ 81+49 =c^2 $$ $$ c = \sqrt{130} $$ $$ \cos{\angle{KJL}} = \boxed{\frac{9}{\sqrt{130}}} $$