Question

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Answer 1

\[area= \pi r ^{2}*\frac{ \theta }{ 360 },\theta is the \angle of the sector\]

Answer 2

\[Area = \frac{rad}{2}r^2\]
this of course is the usual area of a circle: 2pi radians
degrees pi/180 is a good degree to redian conversion

Answer 3

\[\frac{135}{180}\pi~(11)^2\]

Answer 4

so yeah, 2*180 is 360 and there we got it :)