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  2. Binomial theorem - Wikipedia

    en.wikipedia.org/wiki/Binomial_theorem

    Expanding (x + y) n yields the sum of the 2 n products of the form e 1 e 2... e n where each e i is x or y. Rearranging factors shows that each product equals x n−k y k for some k between 0 and n. For a given k, the following are proved equal in succession: the number of terms equal to x n−k y k in the expansion; the number of n-character x ...

  3. Equation xy = yx - Wikipedia

    en.wikipedia.org/wiki/Equation_xy_=_yx

    "x^y = y^x - commuting powers". Arithmetical and Analytical Puzzles. Torsten Sillke. Archived from the original on 2015-12-28. dborkovitz (2012-01-29). "Parametric Graph of x^y=y^x". GeoGebra. OEIS sequence A073084 (Decimal expansion of −x, where x is the negative solution to the equation 2^x = x^2)

  4. Rotation matrix - Wikipedia

    en.wikipedia.org/wiki/Rotation_matrix

    The sum of the entries along the main diagonal (the trace), plus one, equals 4 − 4(x 2 + y 2 + z 2), which is 4w 2. Thus we can write the trace itself as 2w 2 + 2w 2 − 1; and from the previous version of the matrix we see that the diagonal entries themselves have the same form: 2x 2 + 2w 2 − 1, 2y 2 + 2w 2 − 1, and 2z 2 + 2w 2 − 1. So ...

  5. Sum of normally distributed random variables - Wikipedia

    en.wikipedia.org/wiki/Sum_of_normally...

    To determine the value (), note that we rotated the plane so that the line x+y = z now runs vertically with x-intercept equal to c. So c is just the distance from the origin to the line x + y = z along the perpendicular bisector, which meets the line at its nearest point to the origin, in this case ( z / 2 , z / 2 ) {\displaystyle (z/2,z/2)\,} .

  6. List of common coordinate transformations - Wikipedia

    en.wikipedia.org/wiki/List_of_common_coordinate...

    Let (x, y, z) be the standard Cartesian coordinates, and (ρ, θ, φ) the spherical coordinates, with θ the angle measured away from the +Z axis (as , see conventions in spherical coordinates). As φ has a range of 360° the same considerations as in polar (2 dimensional) coordinates apply whenever an arctangent of it is taken. θ has a range ...

  7. Binomial coefficient - Wikipedia

    en.wikipedia.org/wiki/Binomial_coefficient

    As there is zero X n+1 or X −1 in (1 + X) n, one might extend the definition beyond the above boundaries to include () = when either k > n or k < 0. This recursive formula then allows the construction of Pascal's triangle , surrounded by white spaces where the zeros, or the trivial coefficients, would be.

  8. List of mathematic operators - Wikipedia

    en.wikipedia.org/wiki/List_of_mathematic_operators

    In mathematics, an operator or transform is a function from one space of functions to another. Operators occur commonly in engineering, physics and mathematics. Many are integral operators and differential operators.

  9. Symmetry of second derivatives - Wikipedia

    en.wikipedia.org/wiki/Symmetry_of_second_derivatives

    The two iterated integrals are therefore equal. On the other hand, since f xy (x,y) is continuous, the second iterated integral can be performed by first integrating over x and then afterwards over y. But then the iterated integral of f yx − f xy on [a,b] × [c,d] must vanish.