Question

Giúp mình giải câu 13 với 😭 đang gấp lắm ạ huhu

Answer 1

13;
A(-2;1); B(3;-1); C(2;3)

\(AB=\sqrt{\left(3+2\right)^2+\left(-1-1\right)^2}=\sqrt{29}\)

\(AC=\sqrt{\left(2+2\right)^2+\left(3-1\right)^2}=2\sqrt{10}\)

\(BC=\sqrt{\left(2-3\right)^2+\left(3+1\right)^2}=\sqrt{17}\)

\(cosA=\dfrac{AB^2+AC^2-BC^2}{2\cdot AB\cdot AC}=0.76\)

=>sinA=0,65

=>\(S_{ABC}=\dfrac{1}{2}\cdot AB\cdot AC\cdot sinA=\dfrac{13\sqrt{290}}{20}\left(cm^2\right)\)