Hướng dẫn giải Bài 1 (Trang 34 SGK Toán Hình học 11)

Cho lục giác đều ABCDEF có tâm O. Tìm ảnh của tam giác AOF a) Qua phép tịnh tiến theo vectơ <math xmlns="http://www.w3.org/1998/Math/MathML"><mover><mrow><mi>A</mi><mi>B</mi><mo> </mo></mrow><mo>→</mo></mover></math> b) Qua phép đối xứng qua đường thẳng BE c) Qua phép quay tâm O góc <math xmlns="http://www.w3.org/1998/Math/MathML"><mn>120</mn><mo>°</mo></math> Giải: <img class="wscnph" src="https://static.colearn.vn:8413/v1.0/upload/library/25022022/anh-chup-man-hinh-2022-02-25-luc-190533-RxvZrt.png" /> a) Ta có:   <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>T</mi><mover><mrow><mi>A</mi><mi>B</mi></mrow><mo>→</mo></mover></msub><mo> </mo><mo>:</mo><mo> </mo><mi>A</mi><mo> </mo><mo>↦</mo><mi>B</mi><mo> </mo></math>                          <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>O</mi><mo> </mo><mo>↦</mo><mi>C</mi><mo> </mo></math>                          <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>F</mi><mo> </mo><mo>↦</mo><mi>O</mi><mo> </mo></math> Suy ra: <math xmlns="http://www.w3.org/1998/Math/MathML"><mo>△</mo><mi>A</mi><mi>O</mi><mi>F</mi><mo> </mo><mo>→</mo><mo>△</mo><mi>B</mi><mi>C</mi><mi>O</mi><mo> </mo></math> b)  <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>Đ</mi><mrow><mi>B</mi><mi>E</mi></mrow></msub><mo>:</mo><mo> </mo><mi>A</mi><mo>↦</mo><mi>C</mi><mo> </mo></math>               <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>F</mi><mo> </mo><mo>↦</mo><mi>D</mi><mo> </mo></math>               <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>O</mi><mo> </mo><mo>↦</mo><mi>D</mi><mo> </mo></math> <math xmlns="http://www.w3.org/1998/Math/MathML"><mo>△</mo><mi>A</mi><mi>O</mi><mi>F</mi><mo> </mo><mo>→</mo><mo>△</mo><mi>C</mi><mi>D</mi><mi>O</mi><mo> </mo></math> c)   <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>Q</mi><mfenced><mrow><mi>O</mi><mo>,</mo><mo> </mo><mn>120</mn><mo>°</mo></mrow></mfenced></msub><mo> </mo><mo>:</mo><mo> </mo><mi>A</mi><mo> </mo><mo>↦</mo><mi>E</mi><mo> </mo></math>                        <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>F</mi><mo> </mo><mo>↦</mo><mo> </mo><mi>D</mi><mo> </mo></math> <math xmlns="http://www.w3.org/1998/Math/MathML"><mo>△</mo><mi>A</mi><mi>O</mi><mi>F</mi><mo> </mo><mo>→</mo><mo>△</mo><mi>E</mi><mi>O</mi><mi>D</mi><mo> </mo></math>