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  2. The meaning of Inverse Matrix - Mathematics Stack Exchange

    math.stackexchange.com/questions/878507

    I will give a basic definition/understanding, one that I learned in introductory Linear Algebra. For a matrix A A, the inverse matrix A−1 A − 1 is a matrix that when multiplied by A A yields the Identity matrix of the vector space. AA−1 = I A A − 1 = I. A−1 A − 1 can be multiplied to the left or right of A, and still yield I I.

  3. 22. Let A A be an invertible n × n n × n matrix. Suppose we interpret each row of A A as a point in Rn R n; then these n n points define a unique hyperplane in Rn R n that passes through each point (this hyperplane does not intersect the origin). Under this geometric interpretation, A−1 A − 1 has an interesting property: the normal vector ...

  4. (The usual meaning of $\nabla^2 f$ is the Laplacian, $\partial^2 f/\partial x_1^2 + \ldots + \partial^2 f ...

  5. In order to find the final input x x we may solve the Leontief Inverse: x = (I − A)−1 ⋅ d x = (I − A) − 1 ⋅ d. So here's my question: Is there a simple rationale behind this inverse? Especially when considering the form: (I − A)−1 = I + A +A2 +A3 …. (I − A) − 1 = I + A + A 2 + A 3 …. What happens if we change an element ...

  6. As soon as you have ar + ms = 1 a r + m s = 1. , that means that r r. is the modular inverse of a a. modulo m m. , since the equation immediately yields ar ≡ 1 (modm) a r ≡ 1 (mod m) . Another method is to play with fractions Gauss's method: 1 7 = 1 × 5 7 × 5 = 5 35 = 5 4 = 5 × 8 4 × 8 = 40 32 = 9 1. 1 7 = 1 × 5 7 × 5 = 5 35 = 5 4 = 5 ...

  7. How to understand quasi-inverse of a function f∘g∘f = f?

    math.stackexchange.com/questions/3494036/how-to-understand-quasi-inverse-of-a...

    One thing I have to explain here is that the "quasi-inverse" does not seem to be a precise terminology and I can't find any information about quasi-inverse in wikipedia or nlab. (I study it because the form of "quasi-inverse" appears in many branches of mathematics, e.g. in category theory, adjoint functors needs to satisfy triangular identity.

  8. What is the difference between inverse and reciprocal?

    math.stackexchange.com/questions/3531287

    Nope, the inverse of a function is not the same as its reciprocal. The reciprocal is what you would multiply by in order to obtain 1. So for the fraction 1 2, this would be 2 1. For the fraction 3 4, this would be 43. For any x, the reciprocal of ex would be 1 ex, because observe ex ⋅ 1 ex = 1. However, the inverse is what you compose with to ...

  9. defining inverse error function - Mathematics Stack Exchange

    math.stackexchange.com/questions/2575011/defining-inverse-error-function

    As a Special Case $\def \erf{\operatorname{erf}}$. Let’s use a more general inverse function implemented called Inverse Gamma Regularized which existed before $2000$ in Mathematica, so it is a well established function.

  10. linear algebra - Intuitive explanation of left- and right-inverse...

    math.stackexchange.com/.../1595853/intuitive-explanation-of-left-and-right-inverse

    A linear functions defined by a matrix never takes any value twice just when it never takes the value $0$ twice. That's when the kernel is just $\ {0\}$. You should be able to connect that situation to the row or column rank. A function has a right inverse just when it's onto (surjective) - it actually takes on every possible value in its range.

  11. What is a modular inverse? - Mathematics Stack Exchange

    math.stackexchange.com/questions/1396947

    1. The notation A−1 A − 1 is only a formal notation for the inverse of A A. Consider for example the case of C = 5 C = 5 and A = 3 A = 3. Then 2 ⋅ 3 mod 5 = 1 2 ⋅ 3 mod 5 = 1, so 2 2 is the modular inverse of 3 3 modulo 5 5. For small moduli it is easy to find the modular inverse of a number by brute-force.