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  2. Speed of light - Wikipedia

    en.wikipedia.org/wiki/Speed_of_Light

    For example, for visible light, the refractive index of glass is typically around 1.5, meaning that light in glass travels at ⁠ c / 1.5 ⁠ ≈ 200 000 km/s (124 000 mi/s); the refractive index of air for visible light is about 1.0003, so the speed of light in air is about 90 km/s (56 mi/s) slower than c.

  3. List of trigonometric identities - Wikipedia

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

    A formula for computing the trigonometric identities for the one-third angle exists, but it requires finding the zeroes of the cubic equation 4x 3 − 3x + d = 0, where is the value of the cosine function at the one-third angle and d is the known value of the cosine function at the full angle.

  4. Trigonometric functions - Wikipedia

    en.wikipedia.org/wiki/Trigonometric_functions

    In this right triangle, denoting the measure of angle BAC as A: sin A = ⁠ a / c ⁠; cos A = ⁠ b / c ⁠; tan A = ⁠ a / b ⁠. Plot of the six trigonometric functions, the unit circle, and a line for the angle θ = 0.7 radians. The points labeled 1, Sec(θ), Csc(θ) represent the length of the line segment from the origin to that point.

  5. Fizeau's measurement of the speed of light in air - Wikipedia

    en.wikipedia.org/wiki/Fizeau's_measurement_of_the...

    At 3 times the speed it was again eclipsed. [3] [4] Given the rotational speed of the wheel and the distance between the wheel and the mirror, Fizeau was able to calculate a value of 2 × 8633m × 720 × 25.2/s = 313,274,304 m/s for the speed of light. Fizeau's value for the speed of light was 4.5% too high. [5] The correct value is 299,792,458 ...

  6. Solution of triangles - Wikipedia

    en.wikipedia.org/wiki/Solution_of_triangles

    Solution of triangles (Latin: solutio triangulorum) is the main trigonometric problem of finding the characteristics of a triangle (angles and lengths of sides), when some of these are known. The triangle can be located on a plane or on a sphere .

  7. Outline of trigonometry - Wikipedia

    en.wikipedia.org/wiki/Outline_of_trigonometry

    The following outline is provided as an overview of and topical guide to trigonometry: Trigonometry – branch of mathematics that studies the relationships between the sides and the angles in triangles. Trigonometry defines the trigonometric functions, which describe those relationships and have applicability to cyclical phenomena, such as waves.

  8. Rømer's determination of the speed of light - Wikipedia

    en.wikipedia.org/wiki/Rømer's_determination_of...

    By timing the eclipses of Jupiter's moon Io, Rømer estimated that light would take about 22 minutes to travel a distance equal to the diameter of Earth's orbit around the Sun. [1] Using modern orbits, this would imply a speed of light of 226,663 kilometres per second, [2] 24.4% lower than the true value of 299,792 km/s. [3]

  9. Snell's law - Wikipedia

    en.wikipedia.org/wiki/Snell's_law

    Refraction of light at the interface between two media of different refractive indices, with n 2 > n 1. Since the velocity is lower in the second medium (v 2 < v 1), the angle of refraction θ 2 is less than the angle of incidence θ 1; that is, the ray in the higher-index medium is closer to the normal.