Skewed Michelson-Morley apparatus In Section $12.3$ arm A of the Michelson-Morley interferometer was assumed to be along the line of motion and arm B perpendicular, and the predicted time difference according to the ether theory was
$$
\Delta \tau=\frac{l}{c}\left(\frac{v^{2}}{c^{2}}\right)
$$
Calculate the expected time difference if $\operatorname{arm} \mathrm{A}$ is at angle $\theta$ to the line of motion through the ether, as shown.