Question

A triangle on the coordinate plane has points located at a (2,5), b (5,9), and c (8,5). What is the area of the triangle. 

Answer 1

Answer:

The area of the triangle is 12 unit²

Step-by-step explanation:

The vertices of the triangle are;

a(2, 5), b(5, 9), and c(8, 5)

The area of a triangle given coordinates can be given by the following determinant;

$\Delta = \dfrac{1}{2}\begin{vmatrix}x_1 & y_1 & 1\\ x_2 & y_2 & 1\\ x_3 & y_3 & 1\end{vmatrix} = \dfrac{1}{2} \left | x_{1}\cdot y_{2} - x_{2}\cdot y_{1} + x_{2}\cdot y_{3} - x_{3}\cdot y_{2} + x_{3}\cdot y_{1} - x_{1}\cdot y_{3}\right |$

Therefore, we have;

$\Delta = \dfrac{1}{2}\begin{vmatrix}2 & 5 & 1\\ 5 & 9 & 1\\ 8 & 5 & 1\end{vmatrix} = \dfrac{1}{2} \left | 2\times 9 - 5\times 5 + 5\times 5 - 8\times 9 + 8\times 5 - 2\times 5 \right |$

Utilizing an online determinant calculator, we have;

$\dfrac{1}{2} \times \left | -12 \right |= 12$

Therefore, the area of the triangle is 12 unit².