Question

[Yang Yang]

Trong mặt phẳng Oxy cho 2 điểm A(0,1);B(-2,0). Tìm ảnh A' ; B' qua phép quay tâm O góc quay 90

Answer 1

[Nguyễn Việt Lâm]

\(\left\{{}\begin{matrix}x_{A'}=0.cos90^0-1.sin90^0=-1\\y_{A'}=0.cos90^0+1.sin90^0=1\end{matrix}\right.\) \(\Rightarrow A'\left(-1;1\right)\)

\(\left\{{}\begin{matrix}x_{B'}=-2.cos90^0-0.sin90^0=0\\y_{B'}=-2.cos90^0+0.sin90^0=0\end{matrix}\right.\) \(\Rightarrow B'\left(0;0\right)\)