We can find the measure of the arc intercepted by the sector by using the formula:
[tex]S=r\theta[/tex]where r is the radius, s is the length of the arc and theta is the angle
From the question, s = 10π and r=12
substitute and solve for theta
[tex]10\pi=12\theta[/tex]Divide both-side by 12
[tex]\theta=\frac{10\pi}{12}=\frac{5\pi}{6}[/tex]The angle is 5π/6 rad
We can convert to degree by multiplying the answer by 180/π
That is;
[tex]\theta=\frac{5\pi}{6}\times\frac{180}{\pi}=150^o[/tex]