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  2. Proofs of trigonometric identities - Wikipedia

    en.wikipedia.org/wiki/Proofs_of_trigonometric...

    Pythagorean identities. Identity 1: The following two results follow from this and the ratio identities. To obtain the first, divide both sides of by ; for the second, divide by . Similarly. Identity 2: The following accounts for all three reciprocal functions. Proof 2: Refer to the triangle diagram above.

  3. Euclid's theorem - Wikipedia

    en.wikipedia.org/wiki/Euclid's_theorem

    Let π(x) be the prime-counting function that gives the number of primes less than or equal to x, for any real number x. The prime number theorem then states that x / log x is a good approximation to π(x), in the sense that the limit of the quotient of the two functions π(x) and x / log x as x increases without bound is 1:

  4. Mathematical proof - Wikipedia

    en.wikipedia.org/wiki/Mathematical_proof

    Then the sum is x + y = 2a + 2b = 2(a+b). Therefore x+y has 2 as a factor and, by definition, is even. Hence, the sum of any two even integers is even. This proof uses the definition of even integers, the integer properties of closure under addition and multiplication, and the distributive property.

  5. Taylor's theorem - Wikipedia

    en.wikipedia.org/wiki/Taylor's_theorem

    v. t. e. In calculus, Taylor's theorem gives an approximation of a -times differentiable function around a given point by a polynomial of degree , called the -th-order Taylor polynomial. For a smooth function, the Taylor polynomial is the truncation at the order of the Taylor series of the function.

  6. Euler's formula - Wikipedia

    en.wikipedia.org/wiki/Euler's_formula

    The original proof is based on the Taylor series expansions of the exponential function e z (where z is a complex number) and of sin x and cos x for real numbers x . In fact, the same proof shows that Euler's formula is even valid for all complex numbers x.

  7. Newton's method - Wikipedia

    en.wikipedia.org/wiki/Newton's_method

    An illustration of Newton's method. In numerical analysis, Newton's method, also known as the Newton–Raphson method, named after Isaac Newton and Joseph Raphson, is a root-finding algorithm which produces successively better approximations to the roots (or zeroes) of a real -valued function. The most basic version starts with a real-valued ...

  8. Geometric series - Wikipedia

    en.wikipedia.org/wiki/Geometric_series

    The geometric series is an infinite series derived from a special type of sequence called a geometric progression, which is defined by just two parameters: the initial term and the common ratio . Finite geometric series have a third parameter, the final term's power.

  9. Descartes' rule of signs - Wikipedia

    en.wikipedia.org/wiki/Descartes'_rule_of_signs

    Proof of Lemma f ( x ) {\displaystyle f(x)} starts at f ( 0 ) = a 0 > 0 {\displaystyle f(0)=a_{0}>0} and ends at f ( + ∞ ) = + ∞ > 0 {\displaystyle f(+\infty )=+\infty >0} , so it must cross the positive x-axis an even number of times (each of which contributes an odd number of roots), and glance (without crossing) the positive x-axis an ...