Hi, there!
________
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The formula is
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Here
» A=Sector Area, or arc length
» r is the radius (it's squared‼)
» θ is the angle
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
Now, we can substitute our parameters, and work out the answer.
Hope the answer - and explanation - made sense,
happy studying!!