(iv) The figure may be replaced by an equivalent trapezoid, on the system explained in § 23.
The os magnum 1, lunar; sc, scaphoid; u, unciform; of the carpus articulates freely m, magnum; td, trapezoid; tm, with the scaphoid.
The trapezium is also sometimes called a " trapezoid," but it will be convenient to reserve this term for a different figure (§ 24).
- The formulae of § 24 for the area of a trapezoid are of special importance in land-surveying.
Then, if we take ordinates Kb, Lg, Mc, Nd, Pf, equal to B'B, GG', C'C, D'D, FF', the figure abgcdfe will be the equivalent trapezoid, and any ordinate drawn from the base to the a LM N P e X top of this trapezoid will be equal to the portion of this ordinate (produced) which falls within the original figure.
U, ulna; R, radius; c, cuneiform; 1, lunar; s, scaphoid; u, unciform; m, magnum; td, trapezoid; tm, trapezium.
The trapezoid and magnum of the carpus, and the cuboid and navicular of the tarsus are distinct.
Um, the figure formed by joining the tops of these ordinates is a trapezoid whose area is h(Iuo -}- ui+u2 -I-