5
Explanation:
You can use Tan(45)=S/5 to solve for S. Tan basically means Opposite/Adjacent. So the opposite side is S and the adjacent side is S. You plug tan(45) into your calc and then multiply it by 5.
Proportion Below
Tan(45)/1 = S/5
You cross multiply to get Tan(45)*5=S
S would be 5
To check you can use the Pythagorean theorem a^2+b^2=c^2
5^2+5^2=

25+25=50