Here's the question you clicked on:
kcla1996
Use the diagram to find cos B as a fraction in simplest form.
Remember \[\cos (\Theta)= \frac{ adjacent }{Hypotenuse }\]
The whole reason I tried to talk you through the sin example was so you would learn this stuff. What can you take from that previous example and apply here? @Dido525 pointed out exactly what you should be looking for, but you need to show us what you're trying and where you're stuck.