Introduction
   In this paper, by using the concept of spherically symmetric Finsler metric, we define the notion of 

-projectively related metrics as an extension of projectively related metrics. We construct some non-trivial examples of 

-projectively related metrics. Let 
F and  

 be two 

-projectively related metrics on a manifold 
M.  We find the relation between the geodesics of 
F and 

  and prove that any geodesic of  
F is a multiple of a geodesic of  

 and the other way around. There are several projective invariants of Finsler metrics, namely, Douglas metrics, Weyl metrics and generalized Douglas-Weyl curvature. We prove that the Douglas metrics, Weyl metrics and generalized Douglas-Weyl metrics are 

-projective invariants.
 
Material and methods
First we obtain the spray coefficients of a spherically symmetric Finsler metric. By considering it, we define 

-projectively related metrics which is a generalization of projectively related Finsler metrics. Then we find the geodesics of two 

-projectively related metrics. We obtain the relation between Douglas, Weyl and generalized Douglas-Weyl curvatures  of two 

-projectively related metrics.
Results and discussion
We find the Douglas curvature, Weyl curvature and generalized Douglas-Weyl curvature of two 

-projectively related Finsler metrics. These calculations tell us that these class of Finsler metrics are 

-projective invariants.
  
Conclusion
The following conclusions were drawn from this research.
	- We prove that the Douglas curvature, Weyl curvature and generalized Douglas-Weyl curvature are 
-projective invariants. 
	-  Let F and  
 be two 
-projectively related metrics on a manifold M.  We show that F is a Berwald metric if and only if 
 is a Berwald metric. ./files/site1/files/64/12.pdf 
 
                     
                    
                    
                    Type of Study:  
Original Manuscript |
                    Subject: 
                    
alg  Received: 2018/10/31 | Revised: 2021/02/16 | Accepted: 2019/07/23 | Published: 2021/01/29 | ePublished: 2021/01/29