How statement and proof provenance work
The first chip identifies the source of the statement or construction; the second identifies the source of its local proof or verification.
- Literature-sourced: the exact statement appears in a cited source; only wording and notation differ.
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These labels describe origin, not correctness: citations and verification chips remain separate evidence.
Signs, monotonicity intervals, and ranges of sine and cosine
Statement
Sine is strictly increasing on each interval and strictly decreasing on each interval . Cosine is strictly decreasing on and strictly increasing on . Both functions have range .
Facts & Assumptions
Given: An integer .
The zero sets, signs on the fundamental intervals, and period follow from The zero sets of sine and cosine and the least positive common period 2 pi.
Quarter-turn values give the endpoint values (Quarter-turn values and shifts by pi/2 and pi).
, , and the mean value theorem converts derivative sign into strict monotonicity (The derivatives of sine and cosine are cosine and minus sine, The mean value theorem, as the case of Cauchy's: for continuous on with and differentiable on there is with ).
Proof
On the open intervals where is positive respectively negative, makes sine strictly increasing respectively decreasing.
On the open intervals where is positive respectively negative, makes cosine strictly decreasing respectively increasing.
The period moves these conclusions to every integer , and the endpoint values in [L2] show both ranges are exactly .
Depends on
- The zero sets of sine and cosine and the least positive common period 2 pi
- Quarter-turn values and shifts by pi/2 and pi
- The derivatives of sine and cosine are cosine and minus sine
- The mean value theorem, as the case $g(x) = x$ of Cauchy's: for $f$ continuous on $[a,b]$ with $a < b$ and differentiable on $(a,b)$ there is $c \in (a,b)$ with $f(b) - f(a) = f'(c)(b-a)$
Used by
- Buffered certified rational phase approximation Algorithm
- Exact success amplification by attenuating the good branch Algorithm
- Szegedy-walk marked-set detection Algorithm
- A real-valued optimum is not a fractional Grover iteration Counterexample
- An invertible derivative at one point does not give a local inverse without C¹ regularity Counterexample
- Antipodal points on a round sphere have many minimizing geodesics Counterexample
- Fidelity and trace-distance inequalities do not imply QRE data processing Counterexample
- I₂(5) admits no crystallographic scaling and no reduced crystallographic root system with that base pairing Counterexample
- Sharp frequency cutoffs have kernels that are not in L1 Counterexample
- The final-time face is not part of the parabolic boundary Counterexample
- Arcsine-weighted inner product on the Chebyshev interval Definition
- Best uniform polynomial error and Chebyshev interpolation operators Definition
- Chebyshev–Gauss–Lobatto collocation grid Definition
- Principal inverse sine and inverse cosine Definition
- The angular path metric, the Euclidean cone and spherical joins Definition
- A circle of circumference ℓ<2π fails CAT(1) Example
- A cycle and an overlong arm: explicit non-positive witnesses Example
- A pure two-strand full twist as an ordered loop Example
- A right circular cylinder is an elementary solid region, presented by two caps and four side quarters Example
- A vector with mixed signs is not a root, while every root has a sign Example
- All meets and joins of the right weak order of A₂ (S₃), with the left order and the inversion sets compared Example
- An indefinite Coxeter form: infinite, but not of affine type Example
- Analytic and nonsmooth data have geometric and algebraic Chebyshev coefficient decay Example
- B-tilde versus C-tilde: the n=2 coincidence and the duality behind the difference Example
- Bₙ and Cₙ define the same Coxeter diagram and the same Coxeter group Example
- Chamber faces and their stabilizers in A₂ Example
- Characteristics of a monomial, an exponential and a tangent Example
- Chebyshev extremal nodes converge to the arcsine equilibrium measure Example
- Chebyshev–Lobatto nodes cluster quadratically at the endpoints Example
- Cylindrical coordinates have absolute Jacobian determinant r on an injective compact box Example
- Deficiencies of the exponential and sine Example
- Degree-one root and Lobatto interpolation norms Example
- Dihedral diagrams I₂(m): Gram determinants, the infinite case, and the low-rank coincidences Example
- Exact Grover rotation for four addresses and one marked item Example
- Exact sine and cosine values at π/10, π/5, and 2π/5 Example
- G2 from I2(6): the scaled realization and its twelve roots Example
- Gram determinants and principal minors of the non-crystallographic types H₃ and H₄ Example
- Link edge lengths versus dihedral mirror angles in type I₂(m) Example
- Midpoint iteration on a small equilateral spherical triangle contracts geometrically to its centre Example
- Normal coordinates on the round sphere Example
…and 92 more results.
Dependency tree · two levels
23 results within two dependency steps of this one, each drawn at its shortest distance from it. An arrow runs from a result to what uses it, so the chart reads left to right and ends at this result, which carries a heavier outline. Every node is a link to that result. Click elsewhere on the chart to enlarge it.
Sources
- NIST Digital Library of Mathematical Functions, Chapter 4 (standard reference, not scraped)
- C. Schmeiser, Introduction to Analysis (standard reference, not scraped)