Logarithms

 In its simplest form, a logarithm answers the question:

How many of one number do we multiply to get another number?

Example

How many 2s do we multiply to get 8?

Answer: 2 × 2 × 2 = 8, so we needed to multiply 3 of the 2s to get 8

So the logarithm is 3

So these two things are the same:

 

 

 

Negative Logarithms

A negative logarithm means how many times to divide by the number. 

Example: What is log₅(0.008) ... ?
1 ÷ 5 ÷ 5 ÷ 5 = 5^-3, so log₅(0.008) = -3

	Number	How Many 10s	Base-10 Logarithm
	.. etc..
	1000	1 × 10 × 10 × 10	log10(1000)	=	3
	100	1 × 10 × 10	log10(100)	=	2
	10	1 × 10	log10(10)	=	1
	1	1	log10(1)	=	0
	0.1	1 ÷ 10	log10(0.1)	=	-1
	0.01	1 ÷ 10 ÷ 10	log10(0.01)	=	-2
	0.001	1 ÷ 10 ÷ 10 ÷ 10	log10(0.001)	=	-3
	.. etc..

The Word

"Logarithm" is a word made up by Scottish mathematician John Napier (1550-1617), from the Greek word logos meaning "proportion, ratio or word" and arithmos meaning "number", ... which together makes "ratio-number" !

—The Relationship Animated—

 

The graph of the logarithm function log_b(x) (blue)

 is obtained by reflecting  the graph of the 

function b^x (red) at the diagonal line (x = y).

 

The graph of the natural logarithm (green) and 

its tangent at x = 1.5 (black) 

The natural logarithm of t agrees with the integral of 1/x dx from 1 to t:

 

The natural logarithm of t is the shaded area 

underneath the graph of the function

 f(x) = 1/x (reciprocal of x).

                                                                         

History of Stem and Leaf Diagram

 

The Stem and Leaf plot was first used by John Tukey around 1977 in a study of volcanos.

John Tukey was a mathematician and statistician who is credited with first using the term software to describe the programs that run on computers.

Ability to organize data for analysis is important.

List of Planar Symmetry Groups

  Classes of discrete planar symmetry groups.  

The symmetry groups are named here by three naming schemes: International notation, orbifold notation, and Coxeter's bracket notation.

There are three kinds of symmetry groups of the plane:

• 2 rosette groups – 2D point groups
• 7 frieze groups – 2D line groups
• 17 wallpaper groups – 2D space groups

Rosette groups

There are two families of discrete two-dimensional point groups, and they are specified with parameter n, which is the order of the group of the rotations in the group.

Family	Intl (orbifold)	Geo [1]	Schönflies	Coxeter	Order	Example
Cyclic symmetry	n (nn)	n	Cn	[n]+	n	5-fold rotation
Dihedral symmetry	nm (*nn)	n	Dn	[n]	2n	4-fold reflection

Frieze groups

The 7 frieze groups, the two-dimensional line groups, with a direction of periodicity are given with five notational names. The Schönflies notation is given as infinite limits of 7 dihedral groups. The yellow regions represent the infinite fundamental domain in each. Simple example images are given as periodic tilings on a cylinder with a periodicity of 6.

[∞,1], IUC (Orbifold) Geo Schönflies Coxeter Fundamental domain Example p1 (∞∞) p1 C∞ [∞,1]+ p1m1 (*∞∞) p1 C∞v [∞,1] [∞+,2], IUC (Orbifold) Geo Schönflies Coxeter Fundamental domain Example p11g (∞x) p.g1 S2∞ [∞+,2+] p11m (∞*) p.1 C∞h [∞+,2]

[∞,2], IUC (Orbifold) Geo Schönflies Coxeter Fundamental domain Example p2 (22∞) p2 D∞ [∞,2]+ p2mg (2*∞) p2g D∞d [∞,2+] p2mm (*22∞) p2 D∞h [∞,2]

Wallpaper groups

The 17 wallpaper groups, with finite fundamental domains, are given by International notation, orbifold notation, and Coxeter notation, classified by the 5 Bravais lattices in the plane: square, oblique (parallelogrammatic), hexagonal (60 degree rhombic), rectangular, and centered rectangular (rhombic).
The p1 and p2 groups, with no reflectional symmetry, are repeated in all classes. The related pure reflectional Coxeter group are given with all classes except oblique.

Square, [4,4], IUC (Orbifold) Geometric Coxeter Fundamental domain p1 (o) p1 [∞+,2,∞+] p2 (2222) p2 [1+,4,4]+ p2gg pgg (22x) pg2g [4+,4+] p2mm pmm (*2222) p2 [1+,4,4] c2mm cmm (2*22) c2 [[4+,4+]] p4 (442) p4 [4,4]+ p4gm p4g (4*2) pg4 [4+,4] p4mm p4m (*442) p4 [4,4] Parallelogrammatic (oblique) p1 (o) p1 [∞+,2,∞+] p2 (2222) p2 [∞,2,∞]+

Hexagonal [6,3], IUC (Orbifold) Geometric Coxeter Fundamental domain p1 (o) p1 [∞+,2,∞+] p2 (2222) p2 [∞,2,∞]+ c2mm cmm (2*22) c2 [∞,2+,∞] p3 (333) p3 [1+,6,3+] p3m1 (*333) p3 [1+,6,3] p31m (3*3) h3 [6,3+] p6 (632) p6 [6,3]+ p6mm p6m (*632) p6 [6,3] Hexagonal [3[3]], p3 (333) p3 [3[3]]+ p3m1 (*333) p3 [3[3]] p31m (3*3) h3 [3[3[3]]+] p6 (632) p6 [3[3[3]]]+ p6mm p6m (*632) p6 [3[3[3]]]

 

List of spherical symmetry groups

 

Spherical symmetry groups are also called point groups in three dimensions, however this article is limited to the finite symmetries.
There are five fundamental symmetry classes which have triangular fundamental domains: dihedral, cyclic, tetrahedral, octahedral, and icosahedral symmetry.
This article lists the groups by Schoenflies notation, Coxeter notation^[1], orbifold notation^[2], and order. John Conway uses a variation of the Schoenflies notation, named by one or two upper case letters, and whole number subscripts. The group order is defined as the subscript, unless the order is doubled for symbols with a plus or minus, "±", prefix.^[3]
Hermann–Mauguin notation (International notation) is also given. The crystallography groups, 32 in total, are a subset with element orders 2, 3, 4 and 6.

Involutional symmetry

There are four involutional groups: no symmetry, reflection symmetry, 2-fold rotational symmetry, and central point symmetry.

Intl Geo [5] Orbifold Schönflies Conway Coxeter Order Fundamental domain 1 1 1 C1 C1 [ ]+ 1 2 2 22 D1 = C2 D2 = C2 [2]+ 2

Intl Geo Orbifold Schönflies Conway Coxeter Order Fundamental domain 1 22 × Ci = S2 CC2 [2+,2+] 2 2 = m 1 * Cs = C1v = C1h ±C1 = CD2 [ ] 2

Cyclic symmetry

There are four infinite cyclic symmetry families, with n=2 or higher. (n may be 1 as a special case)

Intl Geo Orbifold Schönflies Conway Coxeter Order Fundamental domain 2 2 22 C2 = D1 C2 = D2 [2]+ 2 mm2 2 *22 C2v = D1h CD4 = DD4 [2] 4 4 42 2× S4 CC4 [2+,4+] 4 2/m 22 2* C2h = D1d ±C2 = ±D2 [2,2+] 4

Intl Geo Orbifold Schönflies Conway Coxeter Order Fundamental domain 3 4 5 6 n 3 4 5 6 n 33 44 55 66 nn C3 C4 C5 C6 Cn C3 C4 C5 C6 Cn [3]+ [4]+ [5]+ [6]+ [n]+ 3 4 5 6 n 3m 4mm 5m 6mm - 3 4 5 6 n *33 *44 *55 *66 *nn C3v C4v C5v C6v Cnv CD6 CD8 CD10 CD12 CD2n [3] [4] [5] [6] [n] 6 8 10 12 2n 3 8 5 12 - 62 82 10.2 12.2 2n.2 3× 4× 5× 6× n× S6 S8 S10 S12 S2n ±C3 CC8 ±C5 CC12 CC2n / ±Cn [2+,6+] [2+,8+] [2+,10+] [2+,12+] [2+,2n+] 6 8 10 12 2n 3/m 4/m 5/m 6/m n/m 32 42 52 62 n2 3* 4* 5* 6* n* C3h C4h C5h C6h Cnh CC6 ±C4 CC10 ±C6 ±Cn / CC2n [2,3+] [2,4+] [2,5+] [2,6+] [2,n+] 6 8 10 12 2n

Dihedral symmetry

There are three infinite dihedral symmetry families, with n as 2 or higher. (n may be 1 as a special case)

Intl Geo Orbifold Schönflies Conway Coxeter Order Fundamental domain 222 2.2 222 D2 D4 [2,2]+ 4 42m 42 2*2 D2d DD8 [2+,4] 8 mmm 22 *222 D2h ±D4 [2,2] 8

Intl Geo Orbifold Schönflies Conway Coxeter Order Fundamental domain 32 422 52 622 3.2 4.2 5.2 6.2 n.2 223 224 225 226 22n D3 D4 D5 D6 Dn D6 D8 D10 D12 D2n [2,3]+ [2,4]+ [2,5]+ [2,6]+ [2,n]+ 6 8 10 12 2n 3m 82m 5m 12.2m 62 82 10.2 12.2 n2 2*3 2*4 2*5 2*6 2*n D3d D4d D5d D6d Dnd ±D6 DD16 ±D10 DD24 DD4n / ±D2n [2+,6] [2+,8] [2+,10] [2+,12] [2+,2n] 12 16 20 24 4n 6m2 4/mmm 10m2 6/mmm 32 42 52 62 n2 *223 *224 *225 *226 *22n D3h D4h D5h D6h Dnh DD12 ±D8 DD20 ±D12 ±D2n / DD4n [2,3] [2,4] [2,5] [2,6] [2,n] 12 16 20 24 4n

Polyhedral symmetry

There are three types of polyhedral symmetry: tetrahedral symmetry, octahedral symmetry, and icosahedral symmetry, named after the triangle-faced regular polyhedra with these symmetries.

[3,3] Intl Geo Orbifold Schönflies Conway Coxeter Order Fundamental domain 23 3.3 332 T T [3,3]+ = [3+,4,1+] 12 m3 43 3*2 Th ±T [3+,4] = [[3,3]+] 24 43m 33 *332 Td TO [3,3] = [3,4,1+] 24

[3,4] Intl Geo Orbifold Schönflies Conway Coxeter Order Fundamental domain 432 4.3 432 O O [3,4]+ = [[3,3]]+ 24 m3m 43 *432 Oh ±O [3,4] = [[3,3]] 48 [3,5] Intl Geo Orbifold Schönflies Conway Coxeter Order Fundamental domain 532 5.3 532 I I [3,5]+ 60 532/m 53 *532 Ih ±I [3,5] 120