finding the area of a circle

[math fail]

i have something that looks lik a track and i have to figure out the shaded area wich is the track and i cant figur out the circled end it looks kinda like this ( (
i have to do in between the brakets and figure out the area. plz help its due tommorow

 

[pka]

i have something that looks lik a track and i have to figure out the shaded area wich is the track and i cant figur out the circled end it looks kinda like this ( (
i have to do in between the brakets and figure out the area. plz help its due tommorow

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