Question

Find the area of triangle PQR formed by the points P(–5, 7), Q(–4, –5) and R(4, 5).

Answer 1

Here x₁ = –5, x₂ = –4, x₃ = 4 and y₁ = 7, y₂ = –5, y₃ = 5

∴ Area of ΔPQR = `1/2 [x_1(y_2 - y_3) + x_2(y_3 - y_1) + x_3(y_1 - y_2)]`

= `1/2 [-5(-5 - 5) -4(5 - 7) + 4(7 + 5)]`

= `1/2 [-5(-10) - 4(-2) + 4(12)]`

= `1/2 [50 + 8 + 48]`

= `1/2 xx 106`

= 53 sq. units