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The orbital eccentricity of an astronomical object is a parameter that determines the amount by which its orbit around another body deviates from a perfect ... more

In finance, the Sharpe ratio (also known as the Sharpe index, the Sharpe measure, and the reward-to-variability ratio) is a way to examine the performance ... more

Pixels per inch (PPI) (or pixels per centimeter (PPCM)) is a measurement of the pixel density ... more

Calculates the standard deviation (SD) of a series of numbers (x).

In statistics, the standard deviation (SD) is a measure that is used to quantify
... more

Pell’s equation is a Diophantine equation (a polynomial equation in two or more unknowns ).

In Cartesian coordinates, the equation has the form
... more

The Richardson number (Ri) is named after Lewis Fry Richardson (1881 – 1953). It is the dimensionless number that expresses the ratio of potential to ... more

In geometry, the Euler line is a line determined from any triangle that is not equilateral. It passes through several important points determined from the ... more

A horn antenna or microwave horn is an antenna that consists of a flaring metal waveguide shaped like a horn to direct radio waves in a beam. Horns are ... more

Using the Pythagorean theorem, for 3 different screen resolutions:

Using the Diagonal Resolution from the previous formula we calculate the PPI for 3 corresponding screen sizes :

**Results:**

**10.1** inch tablet screen of resolution **1024×600** : **117.5PPI****21.5** inch PC monitor of **1080p** resolution : **102.46PPI****27** inch PC monitor of **1440p** resolution : **108.78PPI**

The Rydberg formula is used in atomic physics to describe the wavelengths of spectral lines of many chemical elements. It was formulated by the Swedish ... more

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PPI can be calculated from knowing the diagonal size of the screen in inches and the resolution in pixels (width and height). This can be done in two steps