increasing a number to the strength which is a positive totality number

The ide of logarithms occurred from that of strength of numbers. If the properties of powers are acquainted to you, you may easily skim v the product below. If not--well, right here are the details. Powers of a number are obtained by multiply it by itself. For instance2.2 can be written 22 "Two squared" or "2 come the second power"2.2.2 = 23 ."Two cubed" or "2 to the 3rd power""2.2.2.2 = 24 "Two come the 4th power" or simply "2 to the 4th"".2.2.2.2.2 = 25 "Two to the 5th power" or merely "2 to the 5th""2.2.2.2.2.2 = 26 "Two come the sixth power" or just "2 to the 6th"" and so on... The number in the superscript is recognized as one "exponent." The distinct names because that "squared" and also "cubed" come due to the fact that a square of side 2 has actually area 22 and also a cube of next 2 has actually volume 23. Similarly, a square of next 16.3 has actually area (16.3)2 and a cube of next 9.25 has volume (9.25)3. Note the usage of parentheses--they space not for sure needed, but they aid make clear what is increased to the 2nd or 3rd power.Quick Quiz:The Greek Pythagoras verified (about 500 BC) the if (a,b,c) room lengths that the sides of a right-angled triangle, with c the longest, then a2 + b2 = c2In a best angles triangle, a = 12, b = 5. Have the right to you guess c? i beg your pardon is larger--23 or 32? 27 or 53?A slight change of one old riddle goes: as I to be going come St. IvesI met a man with 7 wivesEach wife had actually seven sacksEach sack had actually seven catsEach cat had actually seven kitsKits, cats, man, wives--how plenty of were comes from St. Ives?It all requires powers of 7:Man -- 70 = 1Wives-- 71 = 7Sacks-- 72 = 49 (but they room not component of the count)Cats-- 73 = 343Kits-- 74 = 2401 complete count: 1 + 7 + 343 + 2401 = 2752As noted, this is contempt modified from the initial riddle, i beg your pardon asks "how plenty of were going to St. Ives?" The answer is of course just one, the person telling the riddle. Countless listeners however are distracted by the many details given, miss out on the difference and perform the above calculation. Your answer is climate wrong! The well known Indian mathematician Ramanujan to be sick in a hospital (tuberculosis, probably) as soon as he was saw by his friend the mathematician G.H Hardy, who had earlier invited him come England. Hardy later told:I remember when going to watch him when he was ill in ~ Putney. I had ridden in taxi cab number 1729 and remarked the the number seemed to me quite a dull one, and that i hoped it was not negative omen. "No," the replied, "it is a really interesting number; the is the smallest number expressible as the amount of 2 cubes in two different ways."Cubes are third powers. What are they, in this example? try guessing, selections are limited.

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Multiplying powers

Note the (23).(22) = 25since the very first term contributes three factors of 2 and also the 2nd term contributes two--together, 5 multiplications by 2. The exact same will host if "2" is replaced by any type of number. So, if the number is stood for by "x" we get (x3).(x2) = x5and in general (since over there is naught special about 2 and 3 which will not hold for other entirety numbers) (xa).(xb) = x(a+b)where a and also b are any type of whole numbers. The most widely provided powers by entirety numbers, for customers of the decimal system, are of course those of 10101 = 10 ("ten")102 = 100 ("hundred")103 = 1000 ("thousand")104 = 10,000 ("ten thousand"))105 = 100,000 ("a hundreds thousand")106 = 1,000,000 ("a million") keep in mind that right here the "power index" also gives the variety of zeros. For bigger numbers, it supplied to be that in the us 109 = 1,000,000,000 was dubbed "a billion" while in Europe it was dubbed a "milliard" and one had to advance to 1012 to with a "billion." this days the us convention is obtaining ground, however the civilization remains divided between nations whereby the comma denotes what we contact "the decimal point", while the suggest divides huge numbers, e.g. 109 = 1.000.000.000 (in the united state commas would certainly be used). It likewise should be provided that some cultures have assigned names to some various other powers of 10--e.g. The Greeks supplied "myriad" because that 10,000 when the Hebrew holy bible named the "r"vavah," and also in India "Lakh" still method 100,000, while "crore" is 10,000,000. A 9-year old in 1920 coined the surname "Googol" because that 10100, but the native found little use beyond inspiring the surname of a find engine ~ above the world-wide web.

Dividing one power by another

In a manner very similar to the above, we have the right to write (25) / (22) = 23since dividing a strength of 2 through some smaller power way canceling indigenous the numerator a number of factors same to those in the denominator. Writing it the end in detail(2.2.2.2.2) / (2.2) = 2.2.2 here too the number elevated to higher power need not be 2--again, signify it by x--and the powers require not it is in 5 and 2, but can be any kind of two whole numbers, say a and b: (xa) / (xb) = x(a–b) Here but a new twist is added, since subtraction can also yield zero, or even negative numbers. Prior to exploring the direction, the helps rundown a basic course to follow.

Expanding the definition of "Number"

ago at the dim beginnings of humanity, "numbers" simply meant positive entirety numbers ("integers"): one apple, two apples, 3 apples... Straightforward fractions were also found useful--1/2, 1/3 and also so on.Then zero was added, originally from India.Then negative numbers were given complete status--rather than check out subtraction together a different operation, it to be re-interpreted as addition of a an adverse number. Similarly, come every essence x there coincided an "inverse" number (1/x) (many calculators have actually a 1/x switch too). In old Egypt, 5000 year ago, these were the just fractions recognized, and they are because of this still sometimes called "Egyptian fractions." as soon as an Egyptian of that time wanted to to express 3/4, it was presented as (1/2 + 1/4). Sometimes lengthy expressions were needed, e.g 99/100 = 1/2 + 1/4 + 1/5 + 1/25but it always worked. The old Greeks walk further and defined together "rational number" (or "logical" numbers--"rational" originates from Latin) any multiple of such an inverse, for instance 4/13, 22/7 or 355/113. Rational numbers are dense: no matter how close two of them space to every other, one could constantly place another rational number between them--for instance, half their sum is one selection out of many. Decimal fountain which protect against at some size are rational number too, despite decimal fractions having infinite length but with a repeating pattern (0.33333..., 0.575757... Etc.) can always be expressed as rational fractions. Greek philosophers in the early on days of mathematics were therefore surprised to find that regardless of that density, some extra numbers can still "hide" in between rational ones, and could not be represented by any rational number. Because that instance, √2 is that this class, the number who square equates to 2. Many square roots and solutions that equations are likewise of this kind, together is π, the ratio in between the circumference of a circle and also its diameter (denoted through the Greek letter "pi"). Pi has a same approximation in 22/7 and a much better one in 355/113, however its exact value can never be represented by any kind of fraction. Mathematicians watch all the preceding types of number as a single class that "real numbers". Logarithms of optimistic numbers are actual numbers, too. As soon as one writes2 = 100.3010299.. so that 0.3010299.. = log 2(the dots stand for an irregular continuation) one views it together 10 raised to a strength which is some genuine number. Earlier, powers were integers, denoting the variety of times some number to be multiplied by itself. To do the above expression meaningful, that is as such necessary come generalize the concept of increasing a number to some power come where any type of real number can be the strength index.

Logarithms of powers of 10

These room all entirety numbers:101 = 10 so log 10 = 1102 = 100 so log 100 = 2 103 = 1000 so log 1000 = 3 104 = 10,000 therefore log10,000 = 4 105 = 100,000 so log 100,000 = 5 106 = 1,000,000 so log 1,000,000 = 6 this logarithms additionally satisfy the rules we found(xa).(xb) = x(a+b)So if x=10 U = (10a) V = (10b) W = (10(a+b)) = U.Vthen due to the fact that a = log in U b = logV (a+b) = log in Wwe have logV + log U = log (U.V) This relation holds at any time U and V room powers the 10: The logarithm of the product is the sum of the logarithms of the multiply numbers. together demonstrated in the synopsis in the preceding section. As the concept of logarithm is broadened, that property constantly remains. That is what initially made logarithms useful: convert multiplication right into addition. Instead of having to multiply U and also V, we only need include their logarithms and then look because that the number whose logarithm amounts to that sum: that will be the product (U.V).Similarly, (xa) / (xb) = x(a–b)so if x=10, U = (10a) V = (10b) W = (10(a–b)) = U/Vthen in the division we havelogU – log in V = log (U/V) or "the logarithm of the quotient is the difference between the logarithms of the split numbers," e.g. 107 / 104 = 103 i m sorry agrees with 7 – 4 = 3.Division, though, opens up up a new territory: through the very same rule, for circumstances 1040 / 1043 = 10–3 = 0.001And 104 / 104 = 100 = 1 due to the fact that a number is being divided by itself have to equal 1.Indeed, this is regular with the rule, the including or subtracting 1 come the logarithm move its number one decimal come the best of left. Earlier106 = 1,000,000 so log 1,000,000 = 6 105 = 100,000 so log 100,000 = 5 104 = 10,000 so log10,000 = 4 103 = 1000 so log 1000 = 3 102 = 100 so log 100 = 2 101 = 10 so log 10 = 1and currently this can be extended, separating by 10 at every step100 = 1 so log 1 = 010–1 = 0.1 so log 0.1 = –1 10–2 = 0.01 so log 0.01 = –2 10–3 = 0.001 so log in 0.001 = –3 10– 4 = 0.000 1 so log in 0.000 1 = –4 10–5 = 0.000 01 so log 0.000 01 = –5 10–6 = 0.000 001 so log 0.000 001 = –6 The above demonstrates another property the logarithms:Log (VQ) = Q log in VFor the special situation V = 10, logV = 1

Scientific Notation

The quantities with i m sorry scientists work-related are periodically very little or really large. That is then practically (for calculation, and also for using logarithms) to different the number right into two parts--a number indigenous 1 come 10, giving its structure, and also a strength of 10, offering the magnitude. Electric charge, because that instance, is measure up in coulombs: around one coulomb operation each 2nd through a 100-watt lightbulb. That existing is lugged by a huge number of tiny an unfavorable particles, found in any atom and also known as electrons. Each electron tote a charge of q = 1.60219 10–19 coulomb If this were to be written as a decimal fraction, the expression would certainly take about half a line, with 18 zeros adhering to the decimal allude in prior of the far-ranging digits--and a fast look at it would certainly not provide much information, one still would certainly have had actually to counting the zeros. The massive of the electron is likewise smallm = 9.1095 10–29 kgScientific notation simplifies writing such numbers. Yet another example is the rate of light, together decimal number (accuracy to 6 figures) 299,792,000, in scientific notation c = 2.99792 108 meter/second scientific notation additionally makes multiplication and division easier and also less error prone. One multiplies or divides individually the numerical factors, each between 1 and also 10, and also usually sees at a glance if the an outcome is of the right range of magnitude. Separately, one adds with each other all strength exponents of multiplied factors, and subtracts those of split ones, to get the appropriate power of 10 i beg your pardon then appears in clinical notation. The course, in any type of calculation, one should use constant units--it would not perform to mix meters and also inches, or pounds and grams (such inconsistent use apparently resulted in an error which brought about a space probe to Mars to miss out on the planet and get lost). The most common consistent system in physics and technology is the MKS system, measuring street in meters, fixed in kilograms and time in seconds. All other units are established by the choice of these three standards, and also as long as one remains in the MKS system, results conform to systems of that system too (e.g. If power is gift calculated, it constantly comes out in joules).

An example

electrons of the polar aurora ("northern lights") relocate at about 1/5 the velocity that light, in a magnetic field B which close to the ground is around 5 10–5 Tesla (the Tesla is the MKS unit that magnetic field: in ~ the pole of an iron magnet you get about 1 Tesla). The magnetic field causes an electron come spiral approximately the direction that the magnetic pressure ("magnetic field line") v a radius the r = mv/(qB)where v is the component of the velocity perpendicular to the direction the B. If the ingredient perpendicular to B is half the full velocity (i.e c/10), what is r?We have m = 9.1095 10–29 Kg v = 2.99791 107 m/sec (= 0.1 c) q = 1.60219 10–19 coulomb B = 5 10–5 TeslaCollecting every numerical factors, and also rounding turn off to 3 decimals(9.11).(3.00)/<(1.6).(5)> = 3.42Collecting all exponents(– 29+7) – (–19 – 5) = (– 22) – (– 24) = +2The radius is as such 3.42 102 meter or 342 meters. The is the stimulate of the radius of a an extremely thin auroral ray, watched from the ground. Given that the ground indigenous which aurora is usually regarded is 100 kilometers below the aurora, together a ray must show up as very thin indeed.Next section: (M-15) elevating one strength to Another and a graphic use of logarithms.Back come the master List Timeline Glossary math indexAuthor and also Curator: Dr.

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David P. SternMail to Dr.Stern: stargaze("at" symbol)ptcouncil.net .Updated 9 November 2007, edited 28 October 2016