The Draughtsman's Handbook of Plan and Map Drawing / Including instructions for the preparation of engineering, architectural, and mechanical drawings.

by George G. André

A = a² sin. β sin. θ2 sin. (β + θ).

To find by logarithms the area in acres and decimals of an acre,

Log. A = 2 log. a + log. sin. β + log. sin. θ - log. sin. (β + θ) - 15·30103.

When the three sides are known, a b c being the three sides and s their half sum,

A = √s(s - a)(s - b)(s - c).

To find by logarithms the area in acres and decimals of an acre,

Log. A = log. s + log. (s - a) + log. (s - b) + log. (s - c)2 - 5.

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Inclined Measure.

Table showing the Reduction in Links and Decimals of a Link to be made per Chain for every Half Degree of Inclination from 3° to 30°.