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Answer:
 1. area DEF = 2π cm²
 2. arc JK = 2π cm
Step-by-step explanation:
1. The area is given by ...
 A = 1/2r²θ . . . . . where r is the radius and θ is the central angle in radians
Your sector has an area of ...
 A = (1/2)(3 cm)²(80(π/180)) = (1/2)(9 cm²)(4/9π)
 A = 2π cm²
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2. The length of an arc is ...
 s = rθ . . . . . . . where r is the radius and θ is the central angle in radians
 s = (5 cm)(72(π/180)) = (5 cm)(2/5π)
 s = 2π cm . . . arc length
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Additional comment
There are π radians in 180°, so an angle in degrees can be converted to an angle in radians by multiplying by π/180°. (The units of degrees cancel, leaving a pure number. "Radians" have no units.)
