We can use trigonometric functions to determine how far it is across the lake.
Here, use tangent of angle A:
[tex]\begin{gathered} \tan 40^o=\frac{a}{630} \\ 0.839=\frac{a}{630} \\ 0.839\times630=a \\ 528.632=a \end{gathered}[/tex]
Thus, the lake is 529 yards across.
