Let φ be a formula of degree k + 1 ; then we can write it as

Let φ be a net on X based on the directed set D and let A be a subset of X, then φ is said to be frequently in ( or cofinally in ) A if for every α in D there exists some β ≥ α, β in D, so that φ ( β ) is in A.

Let H be a Hilbert space, and let H * denote its dual space, consisting of all continuous linear functionals from H into the field R or C. If x is an element of H, then the function φ < sub > x </ sub >, defined by

Let φ ( ξ, η, ζ ) be an arbitrary function of three independent variables, and let the spherical wave form F be a delta-function: that is, let F be a weak limit of continuous functions whose integral is unity, but whose support ( the region where the function is non-zero ) shrinks to the origin.

Let ρ, θ, and φ be spherical coordinates for the source point P. Here θ denotes the angle with the vertical axis, which is contrary to the usual American mathematical notation, but agrees with standard European and physical practice.

Let G and H be groups, and let φ: G → H be a homomorphism.

Let a sphere have radius r, longitude φ, and latitude θ.

Let φ range from 0 to 2π, and let θ range from 0 to π / 2.

Let there be a set of differentiable fields φ defined over all space and time ; for example, the temperature T ( x, t ) would be representative of such a field, being a number defined at every place and time.

Let the action be invariant under certain transformations of the space – time coordinates x < sup > μ </ sup > and the fields φ

Let B contains all the sentences of A except ¬ φ.

Let ρ denote the number density of electrons, and φ the electric potential.

Let U be an open set in R < sup > n </ sup > and φ: U → R < sup > n </ sup > an injective differentiable function with continuous partial derivatives, the Jacobian of which is nonzero for every x in U. Then for any real-valued, compactly supported, continuous function f, with support contained in φ ( U ),

Let U be a measurable subset of R < sup > n </ sup > and φ: U → R < sup > n </ sup > an injective function, and suppose for every x in U there exists < span > φ '</ span >( x ) in R < sup > n, n </ sup > such that φ ( y ) = φ ( x ) + < span > φ '</ span >( x ) ( y − x ) + o (|| y − x ||) as y → x.

Let φ: X → Y be a continuous and absolutely continuous function ( where the latter means that ρ ( φ ( E )) = 0 whenever μ ( E ) = 0 ).

* Let I be any directed set with a greatest element m. The direct limit of any corresponding direct system is isomorphic to X < sub > m </ sub > and the canonical morphism φ < sub > m </ sub >: X < sub > m </ sub > → X is an isomorphism.

Let F and G be two sheaves on X with values in the category C. A morphism φ: G → F consists of a morphism φ ( U ): G ( U ) → F ( U ) for each open set U of X, subject to the condition that this morphism is compatible with restrictions.

Let ( m, n ) be a pair of amicable numbers with m < n, and write m = gM and n = gN where g is the greatest common divisor of m and n. If M and N are both coprime to g and square free then the pair ( m, n ) is said to be regular, otherwise it is called irregular or exotic.

Let M be a smooth manifold and let x be a point in M. Let T < sub > x </ sub > M be the tangent space at x.

Let M be a smooth manifold and let x be a point in M. Let I < sub > x </ sub > be the ideal of all functions in C < sup >∞</ sup >( M ) vanishing at x, and let I < sub > x </ sub >< sup > 2 </ sup > be the set of functions of the form, where f < sub > i </ sub >, g < sub > i </ sub > ∈ I < sub > x </ sub >.

Let M be a smooth manifold and let f ∈ C < sup >∞</ sup >( M ) be a smooth function.

Let r be a non zero real number and let the r < sup > th </ sup > power mean ( M < sup > r </ sup > ) of a series of real variables ( a < sub > 1 </ sub >, a < sub > 2 </ sub >, a < sub > 3 </ sub >, ... ) be defined as

Let M be a ( pseudo -) Riemannian manifold, which may be taken as the spacetime of general relativity.

Let M and N be ( left or right ) modules over the same ring, and let f: M → N be a module homomorphism.

Let M be an n × n Hermitian matrix.

Let P < sup >− 1 </ sup > DP be an eigendecomposition of M, where P is a unitary complex matrix whose rows comprise an orthonormal basis of eigenvectors of M, and D is a real diagonal matrix whose main diagonal contains the corresponding eigenvalues.

Let ( M, g ) be a Riemannian manifold and ƒ: M < sup > m </ sup > → R < sup > n </ sup > a short C < sup >∞</ sup >- embedding ( or immersion ) into Euclidean space R < sup > n </ sup >, where n ≥ m + 1.

Let M and N be smooth manifolds and be a smooth map.

* Let H be a group, and let G be the direct product H × H. Then the subgroups

" Let X be the unit Cartesian square ×, and let ~ be the equivalence relation on X defined by ∀ a, b ∈ (( a, 0 ) ~ ( a, 1 ) ∧ ( 0, b ) ~ ( 1, b )).

First proof: Let be an × matrix whose column rank is.

Let be any basis for the column space of and place them as column vectors to form the × matrix.

Second proof: Let be an × matrix whose row rank is.

Third proof: Let be an × matrix.

Let X and Y be objects of a category D. The product of X and Y is an object X × Y together with two morphisms

Let ( S, f ) be a game with n players, where S < sub > i </ sub > is the strategy set for player i, S = S < sub > 1 </ sub > × S < sub > 2 </ sub > ... × S < sub > n </ sub > is the set of strategy profiles and f =( f < sub > 1 </ sub >( x ), ..., f < sub > n </ sub >( x )) is the payoff function for x S. Let x < sub > i </ sub > be a strategy profile of player i and x < sub >- i </ sub > be a strategy profile of all players except for player i. When each player i < nowiki >

Let the curve be a unit speed curve and let t = u × T so that T, u, t form an orthonormal basis: the Darboux frame.

Let A be an m × n matrix, with column vectors v < sub > 1 </ sub >, v < sub > 2 </ sub >, ..., v < sub > n </ sub >.

Let M be a real n × n symmetric matrix.

Let M be a 2n × 2n matrix with real entries.

Let K be a field, and let A be a vector space over K equipped with an additional binary operation from A × A to A, denoted here by · ( i. e. if x and y are any two elements of A, x · y is the product of x and y ).

Let M × M be the Cartesian product of M with itself.

Let be the sheaf of germs of smooth functions on M × M which vanish on the diagonal.

Let X be a g-dimensional torus given as X = V / L where V is a complex vector space of dimension g and L is a lattice in V. Then X is an abelian variety if and only if there exists a positive definite hermitian form on V whose imaginary part takes integral values on L × L.

Let A be an m × n matrix and k an integer with 0 < k ≤ m, and k ≤ n. A k × k minor of A is the determinant of a k × k matrix obtained from A by deleting m − k rows and n − k columns.

Let L < sub > n </ sub > be the space of all complex n × n matrices, and let adX be the linear operator defined by adX Y = for some fixed X ∈ L < sub > n </ sub >.