Question

can any one help please. consider the triangle with vertices A(1,2,3), B(1,-1,9), C(13,4,5) find AB ,AC, ABXAC, what is the area of the triangle?

Answer 1

AB=B-A={0, -3, 6}
AC=C-A={12, 2, 2}

Answer 2

\[
AB \times AC=\{-18, 72, 36\}
\]
Compute the above using determinant.

Answer 3

Area of the triangle ABC is half of the magnitude of AB X AC.

Answer 4

\[
Area = 9 \sqrt{21}

\]

Answer 5

thank you but in ther AC isnt (2,2,2) how did you get it (12,2,2)

Answer 6

AC =C-A=(12,2,2)