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  2. List of trigonometric identities - Wikipedia

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

    Subtracting ⁡ from both sides and dividing by 2 by two yields the power-reduction formula for sine: ⁡ = (⁡ ()). The half-angle formula for sine can be obtained by replacing θ {\displaystyle \theta } with θ / 2 {\displaystyle \theta /2} and taking the square-root of both sides: sin ⁡ ( θ / 2 ) = ± ( 1 − cos ⁡ θ ) / 2 ...

  3. Minute and second of arc - Wikipedia

    en.wikipedia.org/wiki/Minute_and_second_of_arc

    A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol ′, is a unit of angular measurement equal to ⁠ 1 / 60 ⁠ of one degree. [1] Since one degree is ⁠ 1 / 360 ⁠ of a turn, or complete rotation , one arcminute is ⁠ 1 / 21 600 ⁠ of a turn.

  4. Magic angle - Wikipedia

    en.wikipedia.org/wiki/Magic_angle

    θ m is the angle between the space diagonal of a cube and any of its three connecting edges, see image. Another representation of the magic angle is half of the opening angle formed when a cube is rotated from its space diagonal axis, which may be represented as arccos − ⁠ 1 / 3 ⁠ or 2 arctan2 radians ≈ 109.4712° .

  5. Mnemonics in trigonometry - Wikipedia

    en.wikipedia.org/wiki/Mnemonics_in_trigonometry

    Quadrant 3 (angles from 180 to 270 degrees, or π to 3π/2 radians): Tangent and cotangent functions are positive in this quadrant. Quadrant 4 (angles from 270 to 360 degrees, or 3π/2 to 2π radians): Cosine and secant functions are positive in this quadrant. Other mnemonics include: All Stations To Central [6] All Silly Tom Cats [6]

  6. atan2 - Wikipedia

    en.wikipedia.org/wiki/Atan2

    Graph of ⁡ (,) over / In computing and mathematics , the function atan2 is the 2- argument arctangent . By definition, θ = atan2 ⁡ ( y , x ) {\displaystyle \theta =\operatorname {atan2} (y,x)} is the angle measure (in radians , with − π < θ ≤ π {\displaystyle -\pi <\theta \leq \pi } ) between the positive x {\displaystyle x} -axis ...

  7. Small-angle approximation - Wikipedia

    en.wikipedia.org/wiki/Small-angle_approximation

    The quantity 206 265 ″ is approximately equal to the number of arcseconds in a circle (1 296 000 ″), divided by 2π, or, the number of arcseconds in 1 radian. The exact formula is = ⁡ (″) and the above approximation follows when tan X is replaced by X.

  8. Spherical trigonometry - Wikipedia

    en.wikipedia.org/wiki/Spherical_trigonometry

    For example, Todhunter [1] gives two proofs of the cosine rule (Articles 37 and 60) and two proofs of the sine rule (Articles 40 and 42). The page on Spherical law of cosines gives four different proofs of the cosine rule. Text books on geodesy [2] and spherical astronomy [3] give different proofs and the online resources of MathWorld provide ...

  9. Solid angle - Wikipedia

    en.wikipedia.org/wiki/Solid_angle

    [1] Solid angles can also be measured in square degrees (1 sr = (180/ π) 2 square degrees), in square arc-minutes and square arc-seconds, or in fractions of the sphere (1 sr = ⁠ 1 / 4 π ⁠ fractional area), also known as spat (1 sp = 4 π sr). In spherical coordinates there is a formula for the differential,