TheoremBase

Kit for def:sine-cosine-real

The conditions "x is the cosine function" and "x is the sine function" are predicative, and each is the membership condition of a class.

Statement

In the setting of Routine Facts, Continued: Typed Arithmetic, Maps and Predicativity, let n≥1n\ge1 be a metatheoretic number, let x0,…,xn−1x_{0},\dots,x_{n-1} be distinct set variables, and let i<ni<n. Each of the first two clauses states that a condition on x0,…,xn−1x_{0},\dots,x_{n-1} is predicative: expressed by a predicative formula, with x0,…,xn−1x_{0},\dots,x_{n-1} in place of the variables x1,…,xkx_{1},\dots,x_{k} of Conditions Expressed by a Predicative Formula, and Guards (i) and no displayed variables; N\mathbb{N} and its element 11, the addition of N0\mathbb{N}_{0}, the set C\mathbb{C} of complex numbers with its sum and product operations of The Complex Numbers: Pairs of Real Numbers with Their Addition and Multiplication, and the Imaginary Unit (iii), its unit 11 (The Complex Numbers, with the Real Numbers Identified with a Subset of the Complex Numbers (ii)) and its imaginary unit, the map R→C\mathbb{R}\to\mathbb{C} of The Complex Numbers: Pairs of Real Numbers with Their Addition and Multiplication, and the Imaginary Unit (vi), the distance dCd_{\mathbb{C}} on C\mathbb{C}, and R\mathbb{R} with its order ≤\le, its strict order <<, its addition ++ and its element 00 are parameters. In every clause, the cosine function and the sine function are the cosine cos⁡:R→R\cos:\mathbb{R}\to\mathbb{R} and the sine sin⁡:R→R\sin:\mathbb{R}\to\mathbb{R}.

The cosine. The condition "xix_{i} is the cosine function" on x0,…,xn−1x_{0},\dots,x_{n-1} is predicative.

The sine. The condition "xix_{i} is the sine function" on x0,…,xn−1x_{0},\dots,x_{n-1} is predicative.

A class for the cosine. There is a class CC such that, for every class aa, a∈Ca\in C if and only if aa is the cosine function.

A class for the sine. There is a class SS such that, for every class aa, a∈Sa\in S if and only if aa is the sine function.

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