Find the measure of arc AB. 

Answer:
AB = 3π units
Step-by-step explanation:
The arc length is calculated as
AB = circumference of circle × fraction of circle
= 2πr × [tex]\frac{45}{360}[/tex]
= 2π × 12 × [tex]\frac{1}{8}[/tex]
= 24π × [tex]\frac{1}{8}[/tex]
= 3π units