The cosine relation is defined by the length of the adjacent side over the length of the hypotenuse.
So, for triangle ABC, the cosine of B is defined as:
[tex]\cos (B)=\frac{BC}{AB}[/tex]
And for triangle DEF, since the triangles are similar, the cosine of B is equal the cosine of its corresponding angle E:
[tex]\cos (E)=\frac{EF}{DE}[/tex]
So the correct options are the first and fifth ones.
