## A Treatise of Plane and Spherical Trigonometry: In Theory and Practice ; Adapted to the Use of Students ; Extracted Mostly from Similar Works of Ludlam, Playfair, Vince, and Bonnycastle |

### From inside the book

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Page iii

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**Observations**preparatory to the Practical Solution of Plane Triangles Solution of the Cases of Right - angled Triangles Solution of the Cases of Oblique - angled Triangles Mensuration of Heights and Distances 5 7 12 19 27 30 37 41 ... Page xii

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**observed**by former writers , and clears up many difficulties . " * The learner will not be duly qualified to study this treatise with advantage , if he do not possess a competent knowledge of vulgar and decimal fractions , of the ... Page 27

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**Observations**preparatory to the Practical Solution of the Cases of Plane Triangles . 77. Logarithms are a set of artificial numbers adapted to the common or natural numbers , 1 , 2 , 3 , 4 , 5 , & c . for the pur- pose of facilitating ... Page 43

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**observation**. Answer . Height 935.757 yards , greater distance 1631-442 , less distance 1041.125 . 4. From the top of a tower 120 feet high , which was in a line with two trees on the same horizontal plain as its bottom , I took the ... Page 50

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**observe**every an- gle of all the triangles , if the situations will permit ; because the difference between 180 ° and the sum of the three angles of each triangle will enable us , in some measure , to judge of the accuracy of the ...### Common terms and phrases

90 degrees adjacent angle AHDL algebra analogy angle ABC angle ACB Answer arc or angle base centre chord circle comp complement cosecant cosine cotangent Euclid's Elements find the angles find the rest geometry Given the side greater than 90 half the sum half their difference height Hence hypothenuse AC included angle less than 90 logarithmic sines mathematics measured mechanical philosophy negative opposite angle perp perpendicular plane triangle plane trigonometry PROP propositions quadrant AH quantity right-angled spherical triangle right-angled triangle Scholium secant side AB side AC sides and angles sine a sine sine and cosine sine² sines and tangents solution spherical angle spherical triangle ABC spherical trigonometry supplement tables tangent of half theorems third side three angles three sides triangle are given trigono versed sine yards

### Popular passages

Page 12 - In every plane triangle, the sum of two sides is to their difference as the tangent of half the sum of the angles opposite those sides is to the tangent of half their difference.

Page ix - The circumference of every circle is supposed to be divided into 360 equal parts, called degrees ; each degree into 60 equal parts, called minutes ; and each minute into 60 equal parts, called seconds.

Page 23 - Then multiply the second and third terms together, and divide the product by the first term: the quotient will be the fourth term, or answer.

Page 13 - In any triangle, twice the rectangle contained by any two sides is to the difference between the sum of the squares of those sides, and the square of the base, as the radius to the cosine of the angle included by the two sides. Let ABC be any triangle, 2AB.BC is to the difference between AB2+BC2 and AC2 as radius to cos.

Page 87 - The cosine of half the sum of two sides of a spherical triangle is to the cosine of half their difference as the cotangent of half the included angle is to the tangent of half the sum of the other two angles. The sine of half the sum of two sides of a spherical...

Page 74 - The sum of any two sides is greater than the third side, and their difference is less than the third side.