## 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 10

... , and will be divided by BF , a perpen- dicular drawn from the M right angle to the

... , and will be divided by BF , a perpen- dicular drawn from the M right angle to the

**base**, L into two triangles AFB , DFB , similar to the tri . D A angle ABD , and to each CF other ( 8. 6 ) . Also , the two 10 PLANE TRIGONOMETRY . Page 12

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**base**CAB . But if the**base**AB be made radius , the per- pendicular BC becomes the tangent , and the hypothenuse AC the secant of the angle at the**base**CAB . This is manifest from the definitions . PROP . I. 49. In any right - angled ... Page 14

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**base**BC , it will divide the triangle ABC into two right- angled triangles CAD , BAD .. About the centre A , with the ra- dius AD , suppose arcs to be de- scribed on each side of the point D , then DC , DB will be the tan- gents of the ... Page 16

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**base**fall within the triangle , the**base**is to the sum of the other two sides , as their difference is to the difference of the segments of the**base**made by the per- pendicular . Let ABC be the proposed triangle , C the vertex , AB ...### Common terms and phrases

90 degrees adjacent angle AHDL algebra analogy angle ABC angle ACB Answer arc AC arc or angle base centre chord circle comp complement cosecant cosine cotangent Euclid's Elements find the angles find the rest formulæ 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 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.