Find the area of LABC with A(1, –4) and midpoints of sides through A being (2, –1) and (0, –1).
The diagram is given below:
Coordinates of B
2 = (1 + x)/2 [by section formula]
4 = 1 + x
X = 3
–1 = (–4 + y)/2
–2 = (–4 + y)
Y = 2
∴ the coordinates of B(3,2)
Coordinates of C [by section formula]
0 = (1 + x)/2
0 = (1 + x)
x = –1
–1 = (–4 + y)/2
–2 = (–4 + y)
Y = 2
∴ the coordinates of point C are (–1,2)
Now, Area of triangle ABC
= 1/2(x1(y2−y3) + x2(y3−y1) + x3(y1−y2))
= 1/2(1(2–2) + 3(2 + 4)–1(–4–2))
= 1/2(0 + 18 + 6)
= 1/2(24)
= 12 sq unit