Plane trigonometry, and its application to mensuration and land surveying. Accompanied with all the necessary logarithmic and trigonometric tables (1852)
Perkins, George R. (George Roberts), 1812-1876 · New York, D. Appleton · leaf 21
—r = sin. a ; -r-g = cos. b; ^ cos. a; EF AE sin. b. Hence, we have sin. {a-\-b)~ sin. a cos. b + cos. & sin. &.Again, we have , .., xx AG AH-KF AH KF AE AE AE AE AH AF KF EF x...-.. . , -—rr X -r-^r —-^rn X -ttt = cos. a COS. o — sin. « sm. 0.AF AE EF AE For the sine and cosine of a—5, let… … . , ,s EG HF-KF HF AFsin. {a—b) = -jr^ = rT?— = -rT? x KF FEXAE cos. («-&)=_ AE AE AF AE FE sin. a cos. b—cos. a sin. b. AG AH + KE AH AF , KE FE = ^T X AE AF AE FE cos. a cos. b -f sin. a sin. b. Collecting these results, we have sin. {a + b) = sin. a cos. 5 -1- cos. a sin. 5. . . sin. (a—b)=…
Plane trigonometry · Surveying
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