| − | Broadly, speaking algebra concerns 'addition' and 'multiplication', but in the widest possible sense. The objects that are being added or multiplied can be numbers, as in [[number theory]], but they can also can be more general structures such as [[matrix|matrices]], [[function]]s, [[polynomial]]s, [[vector]]s or many others. Concentrating on addition and multiplication does not exclude subtraction or division, since subtraction is formally considered to be addition of an [[additive inverse]] and division is considered to be multiplication by a [[multiplicative inverse]]. That is, subtracting 3 from 2 is rigorously defined to adding the number -2 to 3. Minus two is called the additive inverse of +2. Similarly, dividing 3 by 2 is formally defined in terms of multiplying 3 by (1/2), where 1/2 is the multiplicative inverse of 2. Abstract algebra is the study of [[algebraic structures]] such as [[Group (mathematics)|group]]s, [[Ring (mathematics)|rings]], and [[Field (mathematics)|fields]]. | + | Broadly, speaking algebra concerns 'addition' and 'multiplication', but in the widest possible sense. The objects that are being added or multiplied can be numbers, as in [[number theory]], but they can also can be more general structures such as [[matrix|matrices]], [[function]]s, [[polynomial]]s, [[vector]]s or many others. Concentrating on addition and multiplication does not exclude subtraction or division, since subtraction is formally considered to be addition of an [[additive inverse]] and division is considered to be multiplication by a multiplicative inverse. That is, subtracting 3 from 2 is rigorously defined to adding the number -2 to 3. Minus two is called the additive inverse of +2. Similarly, dividing 3 by 2 is formally defined in terms of multiplying 3 by (1/2), where 1/2 is the multiplicative inverse of 2. Abstract algebra is the study of [[algebraic structures]] such as [[Group (mathematics)|group]]s, [[Ring (mathematics)|rings]], and [[Field (mathematics)|fields]]. |
| − | Geometry is the study of shapes and special relationships. It was defined by [[Felix Klein]] as the study of [[invariant]]s under [[Group (mathematics)|group]]s of [[transformation]]s. For example, the [[Euclidean transformation]]s are [[translation]], [[rotation]] and [[reflection]]. The quantities that are not altered by these transformations are things like angles and distances, so these are the subjects of interest in [[Euclidean geometry]]. Other types of transformations, such as the [[affine transformation]]s, define other types of geometry. Topology is concerned with the connectedness of objects, rather than the distance between them. It is sometimes called 'rubber sheet geometry', as it concerns properties (that is, [[arc]]s between [[node]]s in [[network]]s) of objects that would be preserved even if a diagram of them were to be stretched or shrunk. | + | Geometry is the study of shapes and special relationships. It was defined by Felix Klein as the study of [[invariant]]s under [[Group (mathematics)|group]]s of [[transformation]]s. For example, the Euclidean transformations are [[translation]], [[rotation]] and [[reflection]]. The quantities that are not altered by these transformations are things like angles and distances, so these are the subjects of interest in [[Euclidean geometry]]. Other types of transformations, such as the affine transformations, define other types of geometry. Topology is concerned with the connectedness of objects, rather than the distance between them. It is sometimes called 'rubber sheet geometry', as it concerns properties (that is, [[arc]]s between [[node]]s in [[network]]s) of objects that would be preserved even if a diagram of them were to be stretched or shrunk. |