Question

A area do triangulo, cujo vertices sao (1,2),(3,4)e(4,-1), é igual a:

Answer 1

$Det \left[\begin{array}{ccc}1&2&1\\3&4&1\\4&-1&1\end{array}\right] \\ (1.4.4)+(1.-1.1)+(2.3.1)-(1.4.1)-(2.1.4)-(3.-1.1)\\ 16-1+6-4-8+3\\ 25-13\\ 12\\\\ A= \frac{1}{2} |Det|\\ A= \frac{1}{2} |12|\\ A= \frac{12}{2}\\ A=6$