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  2. Exact trigonometric values - Wikipedia

    en.wikipedia.org/wiki/Exact_trigonometric_values

    The values of sine and cosine of 30 and 60 degrees are derived by analysis of the equilateral triangle. In an equilateral triangle, the 3 angles are equal and sum to 180°, therefore each corner angle is 60°. Bisecting one corner, the special right triangle with angles 30-60-90 is obtained.

  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. Mnemonics in trigonometry - Wikipedia

    en.wikipedia.org/wiki/Mnemonics_in_trigonometry

    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] Add Sugar To Coffee [6] All Science Teachers (are) Crazy [7] A Smart Trig Class [8] All Schools Torture Children [5] Awful Stinky Trig Course [5]

  5. Proofs of trigonometric identities - Wikipedia

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

    This geometric argument relies on definitions of arc length and area, which act as assumptions, so it is rather a condition imposed in construction of trigonometric functions than a provable property. [2] For the sine function, we can handle other values. If θ > π /2, then θ > 1. But sin θ ≤ 1 (because of the Pythagorean identity), so sin ...

  6. Trigonometric tables - Wikipedia

    en.wikipedia.org/wiki/Trigonometric_tables

    A significant improvement is to use the following modification to the above, a trick (due to Singleton [2]) often used to generate trigonometric values for FFT implementations: c 0 = 1 s 0 = 0 c n+1 = c n − (α c n + β s n) s n+1 = s n + (β c n − α s n) where α = 2 sin 2 (π/N) and β = sin(2π/N).

  7. Sine and cosine - Wikipedia

    en.wikipedia.org/wiki/Sine_and_cosine

    In mathematics, sine and cosine are trigonometric functions of an angle.The sine and cosine of an acute angle are defined in the context of a right triangle: for the specified angle, its sine is the ratio of the length of the side that is opposite that angle to the length of the longest side of the triangle (the hypotenuse), and the cosine is the ratio of the length of the adjacent leg to that ...

  8. Trigonometric polynomial - Wikipedia

    en.wikipedia.org/wiki/Trigonometric_polynomial

    A trigonometric polynomial can be considered a periodic function on the real line, with period some divisor of ⁠ ⁠, or as a function on the unit circle.. Trigonometric polynomials are dense in the space of continuous functions on the unit circle, with the uniform norm; [4] this is a special case of the Stone–Weierstrass theorem.

  9. Ptolemy's table of chords - Wikipedia

    en.wikipedia.org/wiki/Ptolemy's_table_of_chords

    For tiny arcs, the chord is to the arc angle in degrees as π is to 3, or more precisely, the ratio can be made as close as desired to ⁠ π / 3 ⁠ ≈ 1.047 197 55 by making θ small enough. Thus, for the arc of ⁠ 1 / 2 ⁠ °, the chord length is slightly more than the arc angle in degrees. As the arc increases, the ratio of the chord to ...