Since the central angle of the sector of the circle is in degrees, we need to convert it to radians, so we are going to use the formula for the area of a circular sector: 
where
is the area
is the radius
is the central angle
We know form our problem that the radius of the sector is 5 in, so
. We also know that the sector's angle is 30°, so 
. Lest replace those value sin our formula:
We can conclude that the expression we should use to calculate the area of the sector in the circle is:
where
We know form our problem that the radius of the sector is 5 in, so
We can conclude that the expression we should use to calculate the area of the sector in the circle is: