EXPLANATION
We can represent this situation as shown as follows:
The expression of Sin(F) is equal to Sin F = Opposite/Hypotenuse = DE/DF
[tex]\sin F=\frac{Opposite}{\text{Hypotenuse}}=\frac{DE}{DF}[/tex]
The equivalent expression would be:
[tex]Cos\text{ D=}\frac{Adjacent}{\text{Hypotenuse}}=\frac{DE}{DF}[/tex]
