Area of a triangle and quadrilateral
Two-dimensional geometry · Mathematics
Study notes
Q: Find the area of triangle (1,2), (4,6), (7,2). Then quadrilateral (0,0), (4,0), (4,3), (0,3). Δ = (1/2)|1(6−2) + 4(2−2) + 7(2−6)| = (1/2)|4 + 0 − 28| = 12. Quadrilateral: it's a 4×3 rectangle = 12. (Or shoelace: same.)