Wentworth, G. A. (George Albert), 1835-1906 · Boston, Ginn & company · leaf 122
ly-ing these Eules we must choose for the middle part that oneof the three parts considered—the two given and the onerequired—which will make the other two either adjacentparts or opposite parts. For example : given a and B; solve the triangle. First, represent the parts as in Fig. 40, and to… … To find c, take co. B asmiddle part; then a andco. c are adjacent parts; andby Rule I., cos B = tan a cot c;whence, tan c = tan a sec B To find A, take co. A as middle part; then a and co. B arethe opposite parts; and by Rule II., cos A = cos a sin B. In like manner, every case of a right spherical…
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