Question

mời các bạn đưa ra đáp án 

Answer 1

Ta có: \(S_{cam}=4S_{hong}\)

Ta có: \(S_{hong}=2S_{xanh}-S_{đen}=2.\pi\left(\dfrac{30}{2}\right)^2.\dfrac{90}{360}-\left(\dfrac{30}{2}\right)^2\)

\(=2.3,14.\dfrac{225}{4}-\dfrac{900}{4}=\dfrac{513}{4}\left(mm^2\right)\)

\(\Rightarrow S_{cam}=4.\dfrac{513}{4}=513\left(mm^2\right)\)