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The slide rule

Chapter 66: TRIGONOMETRICAL FUNCTIONS.
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About This Book

The manual defines the slide rule as an instrument for performing calculations by means of logarithms and provides a concise primer on common logarithms, mantissa and characteristic. It explains the mathematical principle that adding and subtracting logarithms yields products and quotients, and extends this to powers, roots, and trigonometric and algebraic operations. Practical instruction covers the layout and use of scales, slide and cursor, magnifying cursors and special rule types, with examples of routine procedures such as multiplication, division, square and root extraction, and proportional calculations. Descriptions of specialized instruments and applications include engineering tasks like screw-cutting and gear calculations, together with advice on accuracy and practice.

HYDRAULIC EQUIVALENTS.

1 foot head = 0·434 lb. per square inch.
1 lb. per square inch = 2·31 ft. head.
1 imperial gallon = 277·274 cubic inches.
1 imperial gallon = 0·16045 cubic foot.
1 imperial gallon = 10 lb.
1 cubic foot of water = 62·32 lb. = 6·232 imperial gallons.
1 cubic foot of sea water = 64·00 lb.
1 cubic inch of water = 0·03616 lb.
1 cubic inch of sea water = 0·037037 lb.
1 cylindrical foot of water = 48·96 lb.
1 cylindrical inch of water = 0·0284 lb.
A column of water 12 in. long 1 in. square = 0·434 lb.
A column of water 12 in. long 1 in. diameter = 0·340 lb.
Capacity of a 12 in. cube = 6·232 gallons.
Capacity of a 1 in. square 1 ft. long = 0·0434 gallon.
Capacity of a 1 ft. diameter 1 ft. long = 4·896 gallons.
Capacity of a cylinder 1 in. diameter 1 ft. long = 0·034 gallon.
Capacity of a cylindrical inch = 0·002832 gallon.
Capacity of a cubic inch = 0·003606 gallon.
Capacity of a sphere 12 in. diameter = 3·263 gallons.
Capacity of a sphere 1 in. diameter = 0·00188 gallon.
1 imperial gallon = 1·2 United States gallon.
1 imperial gallon = 4·543 litres of water.
1 United States gallon = 231·0 cubic inches.
1 United States gallon = 0·83 imperial gallon.
1 United States gallon = 3·8 litres of water.
1 cubic foot of water = 7·476 United States gallons.
1 cubic foot of water = 28·375 litres of water.
1 litre of water = 0·22 imperial gallon.
1 litre of water = 0·264 United States gallon.
1 litre of water = 61·0 cubic inches.
1 litre of water = 0·0353 cubic foot.
EQUIVALENTS OF POUNDS AVOIRDUPOIS.
10 100 1000 10,000 100,000
qr. lb. cwt. qr. lb. ton cwt. qr. lb. ton cwt. qr. lb. ton cwt. qr. lb.
1 0 10 0 3 16 0 8 3 20 4 9 1 4 44 12 3 12
2 0 20 1 3 4 0 17 3 12 8 18 2 8 89 5 2 24
3 1 2 2 2 20 1 6 3 4 13 7 3 12 133 18 2 8
4 1 12 3 2 8 1 15 2 24 17 17 0 16 178 11 1 20
5 1 22 4 1 24 2 4 2 16 22 6 1 20 223 4 1 4
6 2 4 5 1 12 2 13 2 8 26 15 2 24 267 17 0 16
7 2 14 6 1 0 3 2 2 0 31 5 0 0 312 10 0 0
8 2 24 7 0 16 3 11 1 20 35 14 1 4 357 2 3 12
9 3 6 8 0 4 4 0 1 12 40 3 2 8 401 15 2 24

TRIGONOMETRICAL FUNCTIONS.

RIGHT-ANGLED TRIANGLES.

Sin. A = a
b
Sec. A = b
c
Tan. A = a
c

Cos. A = c
b
Cosec. A = b
a
Cotan. A = c
a

Versin. A = bc
b
. Coversin. A = ba
b
.

Given. Required. Formulæ.
a,b A,C,c Sin. A = a
b
Cos. C = a
b
c = √(b + a)(b − a)
     
a,c A,C,b Tan. A = a
c
Cotan. B = a
c
b = √a2 + c2
     
A,a C,c,b C = 90° − A c = a × Cotan. A b = a
Sin. A
     
A,b C,a,c C = 90° − A a = b × Sin. A c = b × Cos. A
     
A,c C,a,b C = 90° − A a = c × Tan. A b = c
Cos. A
     
OBLIQUE-ANGLED TRIANGLES.

s = ½(a + b + c)

Given.   Formulæ.
A,B,C,a Area= (a2 × Sin. B × Sin. C) ÷ 2 Sin. A
A,b,c ½(c × b × Sin. A)
a,b,c s(sa)(sb)(sc)



Given. Required. Formulæ.
A,C,a c c = aSin. C
Sin. A
A,a,c C Sin. C = c Sin. A
a
a,c,B A Tan. A = a Sin. B
ca Cos. B
a,b,c A Sin. ½A = (sb)(sc)
b × c
Cos. ½A = s(sa)
b × c
;
Tan. ½A = (sb)(sc)
s(sa)



COMPOUND ANGLES.
Sin. (A + B) = Sin. A Cos. B + Cos. A Sin. B.
Sin. (A − B) = Sin. A Cos. B − Cos. A Sin. B.
Cos. (A + B) = Cos. A Cos. B − Sin. A Sin. B.
Cos. (A − B) = Cos. A Cos. B + Sin. A Sin. B.

Tan. (A + B) = Tan. A + Tan. B
1 − Tan. A Tan. B
.

Tan. (A − B) = Tan. A − Tan. B
1 + Tan. A Tan. B
.

SLIDE RULE DATA SLIPS, compiled by C. N. Pickworth, Wh.Sc.

(It is suggested that this page be removed by cutting through the above line, and selected portions of the Sectional Data Slips attached to the back of the Slide Rule.)
¹⁄₃₂ 0·03125
¹⁄₁₆ 0·0625
³⁄₃₂ 0·09375
0·125
⁵⁄₃₂ 0·15625
³⁄₁₆ 0·1875
⁷⁄₃₂ 0·21875
¼ 0·25
⁹⁄₃₂ 0·28125
⁵⁄₁₆ 0·3125
¹¹⁄₃₂ 0·34375
0·375
¹³⁄₃₂ 0·40625
⁷⁄₁₆ 0·4375
¹⁵⁄₃₂ 0·46875
¹⁷⁄₃₂ 0·53125
⁹⁄₁₆ 0·5625
¹⁹⁄₃₂ 0·59375
0·625
²¹⁄₃₂ 0·65625
¹¹⁄₁₆ 0·6875
²³⁄₃₂ 0·71875
¾ 0·75
²⁵⁄₃₂ 0·78125
¹³⁄₁₆ 0·8125
²⁷⁄₃₂ 0·84375
0·875
²⁹⁄₃₂ 0·90625
¹⁵⁄₁₆ 0·9375
³¹⁄₃₂ 0·96875

Circ. of circle = 3·1416 d.

Area „ „ = 0·7854 d2.

Sq. eq. area to cir., s = 0·886 d.

Circle eq. to sq., d = 1·128 s.

Sq. inscbd. in circ., s = 0·707 d.

Circsb. circ. of sq., d = 1·414 s.

Area of ellipse = 0.7854 a × b.

Surface of sphere = 3·1416 d2.

Volume „ „ = 0·5236 d3.

„ „ cone = 0·2618 d2 h.

Radian = 180°
π
= 57·29 deg.

Base of nat. or hyp. log. = e = 2·7183.

Nat. or hyp. log. = com. log. × 2·3026.

g (at London) 32·18 ft. per sec., per sec.

Abs. temp. = deg. F. + 461° = deg. C. + 274°.

C.° = 5
9
(F.° − 32°); F.° = 9
5
C.° + 32°.

Cal. pr.—Ther. units per lb.: Coal, 14,300;

petrol’m, 20,000; coal gas per cu. ft., 700.

Sp. heat:—Wt. iron, 0·1138; C.I., 0·1298;

copper, brass, 0·095; lead, 0·0314.

Inch = 25·4 mil’metres; mil’metre = 0·03937 in.

Foot = 0·3048 metres; metre = 3·2809 feet.

Yard = 0·91438 metre; metre = 1·0936 yards.

Mile = 1·6093 kilomtrs.; kilomtr. = 0·6213 mile.

Sq. in. = 6·4513 sq. cm.; sq. cm. = 0·155 sq. in.

Sq. ft. = 9·29 sq. decmtr.; sq. decmtr. = 0·1076 sq. ft.

Sq. yd. = 0·836 sq. metre; sq. metre = 1·196 sq. yds.

Sq. ml. = 258·9 hectares; hectare = 0·00386 sq. ml.

Cu. in. = 16·386 c. cm.; c. cm. = 0·06102 cu. in.

Cu. ft. = 0·0283 c. metre; c. metre = 35·316 cu. ft.

Grain = 0·0648 gramme; gram. = 15·43 grs.

Ounce = 28·35 grams.; „ = 0·03527 oz.

Pound = 0·4536 kilogm.; kilogm. = 2·204 lb.

Ton = 1·016 tonnes; tonne = 0·9842 ton.

Mile per hr. = 1·466 ft., or 44·7 cm., per sec.

Lb. per cu. in. = 0·0276 kilogram per cu. cm.

Kilogram per cu. cm. = 36·125 lb. per cu. in.

Lb. per cu. ft. = 16·019 kilogm. per cu. mtre.

Grain per gall. = 0·01426 gramme per litre.

Gramme per litre = 70·116 grains per gall.

Ultimate Strength Lb. per Sq. in.
Tens’n. Comp’n.
Wt. iron 50,000 50,000
Cast „ 16,000 95,000
Steel 80,000 70,000
Copper 21,000 50,000
Brass 18,000 10,500
Lead 2,500 7,000
Pine 11,000 6,000
Oak 15,000 10,000
Weight of Metals. Cub. In. Cub. Ft. 12 Cu. In.
Wt. iron 0·277 480 3·33
Cast „ 0·260 450 3·12
Steel 0·283 490 3·40
Copper 0·318 550 3·82
Brass 0·300 520 3·61
Zinc 0·248 430 2·98
Alumin’m 0.096 168 1·16
Lead 0.411 710 4·93
Lb. per sq. in. = 2·31 ft. water = 2·04 in. mercury = 0·0703 kilo. per sq. cm.
Atmosphere = 14·7 lb. per sq. in. = 33·94 ft. water = 1·0335 „ „
Ft. hd. water = 0·433 lb. per sq. in. = 62·35 lb. per sq. ft. = 0·0304 „ „
Cub. ft. of water = 62·35 lb. = 0·0278 ton = 28·315 litres = 7·48 U.S. galls.
Gall. (Imp.) = 277·27 cu. in. = 0·1604 cu. ft. = 10 lb. water = 4·544 litres.
Litre = 1·76 pints = 0·22 gall. = 61 cu. in. = 0·0353 cu. ft. = 0·264 U.S. gall.
Horse-power = 33,000 ft.-lb. per min. = 0·746 kilowatt = 42·4 heat units per min.
Heat unit = 778 ft.-lb. = 1055 watt-sec. = 107·5 kilogrammetres = 0·252 calorie.
Foot-pound = 0·00129 heat unit = 1·36 joules = 0·1383 kilogrammetres.
Kilowatt = 1·34 H.P. = 44,240 ft.-lb. per min. = 3412 heat units per hour.

1. It will be recognised that n is the characteristic of the logarithm of the original number.

2. The special case in which the numerator is 1, 10, or any power of 10 must be treated by the rule for reciprocals (page 27).

3. The possible need for traversing the slide, to change the indices, when using the C and D scales, is not considered as a setting.

4. The reader may be reminded that cross-multiplication of the factors in any such slide rule setting will give a constant product, e.g., 20 × 94·5 = 27 × 70.

5. In this case cross dividing gives a constant quotient, e.g., 8 ÷ 3 = 4 ÷ 1·5. Since the upper scale is now a scale of reciprocals, the ratio is really

O ¼
D 1·5 3

6. These lines should not be brought to the working edge of the scale but should terminate in the horizontal line which forms the border of the finer graduations, their value being read into the calculation by means of the cursor (see page 55).

7. The same principle may be applied to the cursor.

8. Philosophical Transactions of the Royal Society, 1815.


BY THE SAME AUTHOR.
LOGARITHMS FOR BEGINNERS.

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TRANSCRIBER’S NOTES
Page Changed from Changed to
24 the right, so the number of digits in the answer = 3 − 2 × 1 = 2 the right, so the number of digits in the answer = 3 − 2 + 1 = 2
116 grammes, we have the equation, x × Cl.
Ag.Cl.
× a
s
. Hence, the mark
grammes, we have the equation, x = Cl.
Ag.Cl.
× a
s
. Hence, the mark
  • Typos fixed; non-standard spelling and dialect retained.
  • Used numbers for footnotes, placing them all at the end of the last chapter.