Question

A área do triângulo de vértices A(1,2), B(-2,3) e C(3,-4) é:

Answer 1

$\sf{A}=\begin{bmatrix}1&2&1\\-2&3&1\\3&-4&1\end{bmatrix}$

$\sf{det~A=1\cdot(3+4)-2\cdot(-2-3)+1\cdot(8-9)}\\\sf{det~A=7+10-2=15}$

$\sf{A=\dfrac{|det~A|}{2}}\\\huge\boxed{\boxed{\boxed{\boxed{\sf{A=\dfrac{15}{2}=7,5~u\cdot a}}}}}$