Question 853982
Three letters means angle
Two letters means arc length.
XOY=WOV
YZ=ZW means that YOZ=ZOW because R is the same and YOZ=YZ/R and ZOW=ZW/R
So then 
XOY+YOZ=ZOW+WOV
XOZ=ZOV
XOZ/R=ZOV/R
XZ=ZV