# Constants and variables

Applying mathematics in studying of laws of nature and using them in technique, we meet with
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constants
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and
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variables
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. A
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variable
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is a value, which can be changed at the conditions of the considered problem; a
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constant
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cannot be changed at these conditions. The same value
can be a constant for one problem and a variable for the other.

E x a m p l e . An acceleration of a gravity is a constant for the same width of Earth, but it

changes depending on a width, i.e. in other words is a variable.

Variables are marked usually by the last letters of the Latin alphabet:
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x, y, z, …
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and constants – by the first ones:
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a,
b, c, … .
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