We know:
[tex]sin(C)=\frac{h}{a}[/tex]
and
[tex]sin(A)=\frac{h}{c}[/tex]
These expressions have an [tex]h[/tex] term in common. We can combine them if we can find forms of the expressions in terms of [tex]h[/tex]:
[tex]h=a(sin(C))[/tex]
[tex]h=c(sin(A))[/tex]
Now, because [tex]h=h[/tex] (by the reflexive property), we can write:
[tex]a(sin(C))=c(sin(A))[/tex]
This is our answer, A.
