Modular Arithmetic vs Polyhedron and Polyhedra Vol.2

A calculator for arithmetic modulo N. It lets you choose a fixed modulus, and then make lots of calculations without having to press a "mod" button again and again. It also: - follows the order convention; - supports arbitrarily large numbers; - performs fast modular division and exponentiation; - can show a full transcript of your calculation. Modular arithmetic is a "calculus of remainders". It features throughout mathematics and computer science, and has applications from cryptography to barcodes to music. The basic idea is that you choose a modulus N, and then reduce every number to one of the integers 0,1,2,...,N−1 according to what remainder it leaves when dividing by N. For example, using a modulus of 17: 40 ≡ 6 (since 40 ÷ 17 leaves a remainder of 6); 17 ≡ 0 (since 17 ÷ 17 leaves no remainder at all). Arithmetic follows these same rules. Still using a modulus of 17: 15 + 7 ≡ 5 (since 22 ≡ 5); 3 × 9 ≡ 10 (since 27 ≡ 10); 5 ^ 3 ≡ 6 (since 125 ≡ 6). Subtraction and division behave in a way that complements addition and multiplication: −1 ≡ 16 (since 16 + 1 = 17 ≡ 0); 1/2 ≡ 9 (since 9 × 2 = 18 ≡ 1); 4 - 7 ≡ 14 (since 14 + 7 = 21 ≡ 4); 7 ÷ 3 = 8 (since 8 × 3 = 24 ≡ 7). There are no negative numbers or fractions: like −1 and 7 ÷ 3 in the examples above, these are also reduced to one of 0,1,...,N−1. As usual, you cannot divide by zero. You also cannot divide if the right hand side has any common factors with the modulus. If we change our modulus to 10, then the following operations all generate errors: 3 ÷ 20 (since 20 ≡ 0); 7 ÷ 8 (since 8 and 10 have a common factor of 2). Integers can be arbitrarily large. For instance, if we set our modulus to 2305843009213693951 (a Mersenne prime), then: 5 ^ 2305843009213693950 ≡ 1 (by Fermat's little theorem). The code is written carefully, and is backed up by a thorough suite of 186 automated tests. This app supports external keyboards, Siri Shortcuts, and (on iPad) Slide Over, Split View, and multiple windows.

Polyhedron and Polyhedra Volume 2 is a collection of 4 kepler-poinsot polyhedra, 53 uniform star polyhedra, their duals and polyhedral compounds of them. This is also an application which helps you to learn about or explore these mathematical solids. Without knowledge of mathematics or polyhedron, you can easily interact with the 3d solids by this application. So, you will become more familiar with the polyhedrons, and you may enjoy these abstract solids as fascinating formative arts. The main advantage of this app is that it offers a large variety of polyhedral compounds of identical uniform star polyhedra and their duals. By choosing a model, and by setting colors and parameters optionally, you will find various types of 3d shapes including wonderful shapes, mysterious artistic shapes, and strange eccentric shapes, which will be interesting for you. Features: - Swipe or touch gesture will rotate, zoom or move the object. So, you can observe it from various angles or positions. (You can observe it even from inside.) - Switches between showing and hiding each face of the polyhedron, and switches between showing and hiding each component of the compound - Function to display the edges of the polyhedra with selectable thickness and color - For each kepler-poinsot polyhedron, each uniform star polyhedron and each dual of uniform star polyhedron, the app can provide the compound from 14 to 22 kinds (more than 1200 in total). - Many color patterns for the faces of the polyhedron. - Functions to display basic informations about the polyhedron, and to access the wikipedia sites about the related items - Slider controllers to reduce z-fighting (screen flicker) - Save PNG images to camera roll