  An estimate of the jet inclination angle relative to the accreting black
hole's spin can be useful to probe the jet triggering mechanism and the
disc--jet coupling. A Tidal Disruption Event (TDE) of a star by a supermassive
spinning black hole provides an excellent astrophysical laboratory to study the
jet direction through the possibility of jet precession. In this work, we
report a new method to constrain the jet inclination angle $\beta$ and apply it
to the well-sampled jetted TDE Swift J1644+57. This method involves X-ray data
analysis and comparisons of jet models with broad properties of the observed
X-ray dips, to estimate the upper limit of the extent of the contribution of a
plausible jet precession to these X-ray dips. From this limit, we find that
$\beta$ is very likely to be less than $\sim 15^\circ$ for Swift J1644+57. Such
a well-constrained jet inclination angle could be useful to probe the jet
physics. The main advantage of our method is that it does not need to assume an
origin of the observed X-ray dips, and the conclusion does not depend on any
particular type of jet precession (e.g., the one due to the Lense-Thirring
effect) or any specific value of precession frequency or any particular jet
model. These make this method reliable and applicable to other jetted TDEs, as
well as to other jetted accreting systems.
