After reading many articles on this topic, I found that there is no perfect answer depending on the difference in FOV. Nevertheless, I've counted a number of articles written that this is the best way to calculate it. So, I calculated it this way.

 

 

However, I am not sure yet, so I would like to ask everyone  to confirm.

Sorry for bad english. And, thank you for reading this short article

 

.

2 hours ago, justforamoment000 said:

 

After reading many articles on this topic, I found that there is no perfect answer depending on the difference in FOV. Nevertheless, I've counted a number of articles written that this is the best way to calculate it. So, I calculated it this way.

 

 

However, I am not sure yet, so I would like to ask everyone  to confirm.

Sorry for bad english. And, thank you for reading this short article

 

.