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  2. Small-angle approximation - Wikipedia

    en.wikipedia.org/wiki/Small-angle_approximation

    [1] [2] One reason for this is that they can greatly simplify differential equations that do not need to be answered with absolute precision. There are a number of ways to demonstrate the validity of the small-angle approximations. The most direct method is to truncate the Maclaurin series for each of the trigonometric functions.

  3. Tangent half-angle substitution - Wikipedia

    en.wikipedia.org/wiki/Tangent_half-angle...

    The tangent of half an angle is important in spherical trigonometry and was sometimes known in the 17th century as the half tangent or semi-tangent. [2] Leonhard Euler used it to evaluate the integral ∫ d x / ( a + b cos ⁡ x ) {\textstyle \int dx/(a+b\cos x)} in his 1768 integral calculus textbook , [ 3 ] and Adrien-Marie Legendre described ...

  4. Pythagorean trigonometric identity - Wikipedia

    en.wikipedia.org/wiki/Pythagorean_trigonometric...

    Similar right triangles illustrating the tangent and secant trigonometric functions Trigonometric functions and their reciprocals on the unit circle. The Pythagorean theorem applied to the blue triangle shows the identity 1 + cot 2 θ = csc 2 θ, and applied to the red triangle shows that 1 + tan 2 θ = sec 2 θ.

  5. Fáry's theorem - Wikipedia

    en.wikipedia.org/wiki/Fáry's_theorem

    By Euler's formula for planar graphs, G has 3n − 6 edges; equivalently, if one defines the deficiency of a vertex v in G to be 6 − deg(v), the sum of the deficiencies is 12. Since G has at least four vertices and all faces of G are triangles, it follows that every vertex in G has degree at least three.

  6. Erdős–Gallai theorem - Wikipedia

    en.wikipedia.org/wiki/Erdős–Gallai_theorem

    The Erdős–Gallai theorem is a result in graph theory, a branch of combinatorial mathematics.It provides one of two known approaches to solving the graph realization problem, i.e. it gives a necessary and sufficient condition for a finite sequence of natural numbers to be the degree sequence of a simple graph.

  7. Integration by substitution - Wikipedia

    en.wikipedia.org/wiki/Integration_by_substitution

    Integration by substitution can be derived from the fundamental theorem of calculus as follows. Let and be two functions satisfying the above hypothesis that is continuous on and ′ is integrable on the closed interval [,].

  8. Circulant graph - Wikipedia

    en.wikipedia.org/wiki/Circulant_graph

    Every cycle graph is a circulant graph, as is every crown graph with number of vertices congruent to 2 modulo 4.. The Paley graphs of order n (where n is a prime number congruent to 1 modulo 4) is a graph in which the vertices are the numbers from 0 to n − 1 and two vertices are adjacent if their difference is a quadratic residue modulo n.

  9. List of integrals of trigonometric functions - Wikipedia

    en.wikipedia.org/wiki/List_of_integrals_of...

    The following is a list of integrals (antiderivative functions) of trigonometric functions.For antiderivatives involving both exponential and trigonometric functions, see List of integrals of exponential functions.