We will calculate the area of sector APC, then calculate the area of ΔCOP 
and subtract it from the sector and that will leave the area of OCA.  
Go here:

http://www.algebra.com/tutors/students/your-answer.mpl?question=1189421

where I have already calculated ∠APC = 0.6290064738 radians.  The formula 
for a sector is  where θ is in radians.  

So the area of the sector APC is



Now we'll find the area of ΔCOP by Heron's formula:

}

where s represents the semi-perimeter.

The perimeter = CO+OP+CP = 12+11+19 = 42

The semi-perimeter is half of that or s = 21.

} 

}

} 

}

Subtracting the area of ΔCOP from the area of the
sector APC, we get

} cm2.

 Edwin