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Riemann's original use of the explicit formula was to give an exact formula for the number of primes less than a given number. To do this, take F(log(y)) to be y 1/2 /log(y) for 0 ≤ y ≤ x and 0 elsewhere. Then the main term of the sum on the right is the number of primes less than x.
Algebraic expression, a mathematical expression in terms of a finite number of algebraic operations (addition, subtraction, multiplication, division and exponentiation by a rational exponent ) Explicit formulae (L-function), relations between sums over the complex number zeroes of an L-function and sums over prime powers
Formulas for prime-counting functions come in two kinds: arithmetic formulas and analytic formulas. Analytic formulas for prime-counting were the first used to prove the prime number theorem . They stem from the work of Riemann and von Mangoldt , and are generally known as explicit formulae .
In mathematics, Stirling's approximation (or Stirling's formula) is an asymptotic approximation for factorials. It is a good approximation, leading to accurate results even for small values of n {\displaystyle n} .
In mathematics and computational science, the Euler method (also called the forward Euler method) is a first-order numerical procedure for solving ordinary differential equations (ODEs) with a given initial value. It is the most basic explicit method for numerical integration of ordinary differential equations and is the simplest Runge–Kutta ...
Solving for y gives an explicit solution: y = ± 1 − x 2 . {\displaystyle y=\pm {\sqrt {1-x^{2}}}\,.} But even without specifying this explicit solution, it is possible to refer to the implicit solution of the unit circle equation as y = f ( x ) , where f is the multi-valued implicit function.
for + (compare this with formula (3) where + was given explicitly rather than as an unknown in an equation). This is a quadratic equation , having one negative and one positive root . The positive root is picked because in the original equation the initial condition is positive, and then y {\displaystyle y} at the next time step is given by
In linear algebra, Cramer's rule is an explicit formula for the solution of a system of linear equations with as many equations as unknowns, valid whenever the system has a unique solution. It expresses the solution in terms of the determinants of the (square) coefficient matrix and of matrices obtained from it by replacing one column by the ...