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  2. List of trigonometric identities - Wikipedia

    en.wikipedia.org/wiki/List_of_trigonometric...

    These identities are useful whenever expressions involving trigonometric functions need to be simplified. An important application is the integration of non-trigonometric functions: a common technique involves first using the substitution rule with a trigonometric function, and then simplifying the resulting integral with a trigonometric identity.

  3. Proofs of trigonometric identities - Wikipedia

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

    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 ⁡.

  4. Trigonometric substitution - Wikipedia

    en.wikipedia.org/wiki/Trigonometric_substitution

    In this case, an expression involving a radical function is replaced with a trigonometric one. Trigonometric identities may help simplify the answer. [1] [2] Like other methods of integration by substitution, when evaluating a definite integral, it may be simpler to completely deduce the antiderivative before applying the boundaries of integration.

  5. Trigonometric functions - Wikipedia

    en.wikipedia.org/wiki/Trigonometric_functions

    This means that the ratio of any two side lengths depends only on θ. Thus these six ratios define six functions of θ , which are the trigonometric functions. In the following definitions, the hypotenuse is the length of the side opposite the right angle, opposite represents the side opposite the given angle θ , and adjacent represents the ...

  6. Square root of 2 - Wikipedia

    en.wikipedia.org/wiki/Square_root_of_2

    The square root of two forms the relationship of f-stops in photographic lenses, which in turn means that the ratio of areas between two successive apertures is 2. The celestial latitude (declination) of the Sun during a planet's astronomical cross-quarter day points equals the tilt of the planet's axis divided by 2 {\displaystyle {\sqrt {2}}} .

  7. Trigonometry - Wikipedia

    en.wikipedia.org/wiki/Trigonometry

    Trigonometric ratios are the ratios between edges of a right triangle. These ratios depend only on one acute angle of the right triangle, since any two right triangles with the same acute angle are similar. [31] So, these ratios define functions of this angle that are called trigonometric functions.

  8. Ratio estimator - Wikipedia

    en.wikipedia.org/wiki/Ratio_estimator

    The ratio estimator is a statistical estimator for the ratio of means of two random variables. Ratio estimates are biased and corrections must be made when they are used in experimental or survey work. The ratio estimates are asymmetrical and symmetrical tests such as the t test should not be used to generate confidence intervals.

  9. Relative change - Wikipedia

    en.wikipedia.org/wiki/Relative_change

    In any quantitative science, the terms relative change and relative difference are used to compare two quantities while taking into account the "sizes" of the things being compared, i.e. dividing by a standard or reference or starting value. [1] The comparison is expressed as a ratio and is a unitless number.