  We carried out UBVRcIc photometric study of three poorly studied young open
clusters IC 1442, King 21, and Trumpler 7 (Tr 7). We obtained 263, 244, and 128
member stars using Gaia DR2 proper motions and parallaxes in IC 1442, King 21,
and Tr 7, respectively. The reddening, E(B-V), was derived to be 0.54+/-0.04,
0.76+/-0.06, and 0.38+/-0.04 mag for these clusters. The comparison of observed
colour-magnitude diagrams (CMDs) with solar metallicity isochrones yields
log(Age) = 7.40+/-0.30, 7.70+/-0.20, and 7.85+/-0.25 yr and corresponding
distances 2847+/-238, 2622+/-156, and 1561+/-74 pc for IC 1442, King 21, and Tr
7, respectively. The estimated mass function (MF) slopes are found to be
-1.94+/-0.18, -1.54+/-0.32, and -2.31+/-0.29 for IC 1442, King 21, and Tr 7,
respectively. The study of MF slopes determined separately in the inner and the
outer regions of these clusters gives a steeper slope in outer region which
suggests spatial variation in slope and mass segregation in the clusters. We
found evidence of mass segregation after dynamical study in these clusters. The
obtained relaxation time is 74, 26, and 34 Myr for the clusters IC 1442, King
21, and Tr 7, respectively. The mass segregation in IC 1442 may be caused by
early dynamical relaxation. The estimated relaxation time is well below to the
ages of King 21 and Tr 7 which indicates that these clusters are dynamically
relaxed.
