In the figure, YX and YZ are tangents to circle A at points X and Z, respectively.
measure of arc XZ= 140measure of arc XSZ= 220
What is the measure of ∠XYZ ?
When we have two tangents drawn to a circle as above....it sets up the following :
measure XYZ = (1/2) (arc XSZ - arc XZ ) =
(1/2) ( 220 - 140 ) =
(1/ 2) ( 80) =
40°
+490 
