Answer:
cos(∠B) = CB/AB = ED/AD
Step-by-step explanation:
[tex]cosine=\dfrac{adjacent}{hypotenuse}\\\\adjacent=BC\\hypotenuse=AB\\\\\cos B=\dfrac{BC}{AB}\\\\\angle B\cong\angle D,\ \text{therefore}\ \cos B=\cos D.\\\\adjacent=ED\\hypotenuse=AD\\\\\cos B=\cos D=\dfrac{ED}{AD}[/tex]
