Answer:
The measure of arc EBC is 220°
Explanation:
step 1
Find out the measure of angle COB
we know that
m∠COB+m∠DOC=90° -----> given problem
we have that
m∠DOC=m arc DC -----> by central angle
m arc DC=50°
so
m∠DOC=50°
Find m∠COB
m∠COB+50°=90°
m∠COB=40°
step 2
Find out the measure of arc BC
we have that
m arc BC=m∠COB -----> by central angle
m∠COB=40°
therefore
m arc BC=40°
step 3
Find out the measure of arc EBC
we know that
m arc EBC=m arc EB+m arc BC
m arc EB=180° -----> because the diameter divide the circle into two equal parts
so
m arc EBC=180°+40°=220°