The segment AB is:
[tex]\sqrt[]{3^2+4^2}=5[/tex]
So now we can use the sin law to calculate the angle B so:
[tex]\frac{\sin(90)}{5}=\frac{\sin (B)}{3}[/tex]
and we solve for B so:
[tex]\begin{gathered} \sin ^{-1}(\frac{3}{5})=B \\ 36.9º=B \end{gathered}[/tex]
