Question

calcule a area do triangulo (-2,1) (1,5) ( 3,9)

Answer 1

At=D/2

$\left[\begin{array}{ccc}-2&1&1\\1&5&1\\3&9&1\end{array}\right] = D$

D = -(3*5*1)-(9*1*-2)-(1*1*1)+(-2*5*1)+(1*1*3)+(9*1*1)

D = -15+18-1-10+9+9

D= 10

A=10/2

A=5