(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 formulae of § 24 for the area of a **trapezoid** are of special importance in land-surveying.

The trapezium is also sometimes called a " **trapezoid**," but it will be convenient to reserve this term for a different figure (§ 24).

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-