. A treatise on surveying and navigation: uniting the theoretical, the practical, and the educational features of these subjects. g one extremity of the line A, and the otherextremity B. From A, by means of the protractor (or otherwise),make the angle -4=48° 3, and from B, make the angle_£=40° 14. The intersections of the lines AC, BC, will give theangle C, which being measured will be found to be a little morethan a right angle. Take A C in the dividers, and apply it to the scale, and it will befound to be 243 ; and BC will be found to be , if the projec-tion is accurately made; hut no o
. A treatise on surveying and navigation: uniting the theoretical, the practical, and the educational features of these subjects. g one extremity of the line A, and the otherextremity B. From A, by means of the protractor (or otherwise),make the angle -4=48° 3, and from B, make the angle_£=40° 14. The intersections of the lines AC, BC, will give theangle C, which being measured will be found to be a little morethan a right angle. Take A C in the dividers, and apply it to the scale, and it will befound to be 243 ; and BC will be found to be , if the projec-tion is accurately made; hut no one should expect numerical accuracyfrom this mechanical method. N. B. Our figures in the book do not pretend to accuracy, they should bedrawn on paper on a larger scale. BY LOGARITHMS. To find A C. As sin. 91° 43 - - - : AS 376 - - - - : : sin. AB 40° 14 - - - : A (7 243 - - - - Observe, that the sine of 91° 43 is the same as the cosine of 1 ° 66 SURVEYING. To find B C. As sin. 91° 43 - - - : AB376 - - - - : : sin. A 48° 3 - - - : £( - - - EXAMPLE 2, In a plane triangle, given two sides, and an angle opposite one ofthem, to determine the other parts. Let AD=1151. feet, one of the givensides. The angle Z>=31° 17 19, andthe side opposite, From thesedata, we are required to find the otherside, and the other two angles. In this case we do not know whetherA 0 or AE represents , becauseA C=AE. If we take A C for the other given side, then D 0 is theother required side, and J)AC is the vertical angle. If we take AEfor the other given side, then BE is the required side, and DAE isthe vertical angle ; but in such cases we determine both triangles. INSTRUMENTALITY. Draw DE indefinitely—from the point D make the angleD=S1° 17. AD=1751., but call it , which take from thescale. Place one foot of the dividers at D, the other foot will extendto A, thus fi
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Keywords: ., boo, bookcentury1800, booksubjectnavigation, booksubjectsurveying
