Scalar triangle measurements: Area (default) Perimeter Semiperimeter Inradius Circumradius for Triangle or point-list input
TriangleMeasurement[tri, type]
TriangleMeasurement[{{0, 0}, {3, 0}, {3, 4}}, "Semiperimeter"]
→ 6TriangleMeasurement[{{0, 0}, {3, 0}, {0, 4}}, "Area"]
→ 6TriangleMeasurement[{{0, 0}, {b, 0}, {0, h}}, "Area"]
→ Abs[b*h]/2