Question

Очень прошу! Помогите!

Answer 1

$AB (4;-4\sqrt{3});\\ BC (-7;4\sqrt{3});\\ cosa=\frac{4*-7-(4\sqrt{3})^2}{\sqrt{4^2+(4\sqrt{3})^2}*\sqrt{-7^2+(4\sqrt{3})^2}}=\frac{-76}{8\sqrt{97}}\\ AC=\sqrt{8^2+\sqrt{97}^2-2*8*\sqrt{97}*\frac{-76}{8\sqrt{97}}} =\sqrt{313}\\ 97=64+313-2*8*\sqrt{313}*cosBAC\\ cosBAC=\frac{35}{2\sqrt{313}}\\ BAC=arccos(\frac{35}{2\sqrt{313}})$