Why the molecular shape of ClF3 is T-Shape,but not triangular planner?See the attachment for full and complete question.

To find the shape of the compound its steric number must be calculated as the type of hybridization and shapes depends on it.
The formula used to calculate the steric number is as follows:
Steric number = Number of bond atoms + Number of lone pairs

In , it has three Cl-F covalent bonds. Thus it is confirmed as it has 3 pairs of bond electrons and 2 pairs of lone electrons and together has 5 electron pairs as given in the attachment.
Thus the steric number of  is 3+ 2 = 5. As the steric number is 5, the hybridization is .
As the steric number is 5, the compound has trigaonal bipyramidal with two positions occupied by lone pairs. Due to this it has a bent-T shaped structure.