Verified calculation capability

Arctangent Calculation Capability

Principal arctan(x) for any finite real x, returning degrees and radians with verification. · Math

Capability ID math.arctan · version 1.0.7

Open calculator REST API MCP Evidence Evidence JSON CVP Manifest Review policy

Model

Definition

Definition: θ = arctan(x) = tan⁻¹(x)
Degrees: θ° = arctan(x) × 180/π
Right triangle: θ = arctan(opposite / adjacent)

Inputs / Outputs

Canonical symbols for this capability. Agent schemas remain the contract.

Symbol	Quantity	Unit	Role
`x`	Any finite real. Share-URL alias: xInput	—	input
`xInput`	Share-URL alias for x	—	input
`deg`	—	—	output
`rad`	—	—	output
`exact`	—	—	output

Assumptions / Validity

Declared scope for this capability. Do not use it outside this domain.

Assumptions

Real inverse tangent with principal branch (−π/2, π/2) (NIST DLMF §4.23(ii)). Infinity is not accepted as an input.
Opposite/adjacent in the UI is a right-triangle length convenience (opposite ≥ 0, adjacent > 0, same unit). It is not atan2. The published engine remains single-argument arctan(x). Use Decimal for a signed ratio, and Tan for the forward map.
When x is exactly a listed common value (0, ±1/√3, ±1, ±√3), the engine returns the exact algebraic angle such as 45° = π/4. Nearby floats are not snapped.

Example

One numerical check. The calculator page holds worked steps and FAQ.

arctan(1) = 45° = π/4

Open this example in the calculator

Trust

CVP VERIFIED · CVP protocol 1.0.0-proposed · Core assurance. Computational verification is defined by CVP. Supplemental domain review (internal) and named expert review are defined by the Review policy and do not by themselves determine CVP conformance.

CVP: CVP VERIFIED · CVP protocol 1.0.0-proposed · Core assurance· View Manifest · CVP overview · Specification
Assurance: Core
Declared partition coverage: PASS · 3/3 declared partitions (arctan, invalid-domain, xcal)
Calculation version: 1.0.7
Verification: 10/10 calculation tests · 7/7 legacy golden · 3/3 legacy boundary
Production surface contract: 3/3
Versions: Calculation 1.0.7 · CVP protocol 1.0.0-proposed
CVP identity: 8/8 property · digest cf317536e8dd
Reference: O1 model · O3 expected_values · O3 numerical_behavior · O2 expected_values · O2 numerical_behavior
Interfaces: PASS · UI (SSR) / REST / MCP / URL→result→graph
Success 1/1. Integration: URL → SSR result → Live graph current point (4/4). Hydration/slider/history are URL-canonical contracts, not a live browser session.
CVP suite: 9/9 golden · 3/3 CVP boundary · 3/3 invalid · 8/8 property · 3/3 metamorphic · 4/4 round-trip · 21/21 O3 · 1/1 cross-interface · 4/4 cross-calculator · 4/4 URL→result→graph · 1/1 CVP contract
Supplemental domain review: Not performed
Named expert review: Not performed
Version lock: Supported (409 VERSION_MISMATCH)
Artifact consistency: Build verified · 1.0.7 (workspace artifacts agree)
Review-policy tier: Engine tested — catalog token engine_tested; supplemental; not CVP status

This calculator CURRENT · Public schema 1.0.7 matches · Semantic contract ✓ · Production attested · Public/cache ✓ · Origin ✓

Call this capability

Human page, REST, and MCP share the same engine and calculation_version. Build verified hashes workspace artifacts only. After deploy, attest:production GETs canonical URLs twice — the public/cached view an Agent actually hits, and origin — including every /capabilities/{id} HTML page. Public Capability HTML version must match catalog before production attestation passes. Live Trust rows above fetch /.well-known/calculatorx-production-attestation.json and the output schema const. Build hashes: release integrity. That proves currently published page / engine / schema / evidence / MCP agree — not that a historical version is independently immutable. Reference Calculation Standard — Production surface contract 3/3.

Tool id: arctan
Engine: arctan
REST: POST /api/v1/calc/arctan
MCP: execute_calculation with capability_id: "math.arctan"
Agent input schema: Canonical (MCP / Agent)
Output schema: JSON Schema (latest)
Versioned input schema: Immutable pin (1.0.7)
Versioned output schema: Immutable pin (1.0.7)

References

Human-readable sources plus CVP reference evidence classes.

Sources

NIST Digital Library of Mathematical Functions, Chapter 4 — Elementary Functions
NIST DLMF §4.23 — Inverse trigonometric functions; principal values
CalculatorX mathematical conventions — Principal branch; exact-value recognition; ratio mode is UI-only

Reference evidence classes: O1 model · O3 expected_values · O3 numerical_behavior · O2 expected_values · O2 numerical_behavior

Try with an agent

Inspect this capability via same-origin MCP, then call execute_calculation.

curl -sS -X POST 'https://www.calculatorx.com/mcp' \
  -H 'Content-Type: application/json' \
  -H 'MCP-Protocol-Version: 2026-07-28' \
  -H 'Mcp-Method: tools/call' \
  -H 'Mcp-Name: inspect_capability' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"inspect_capability","arguments":{"capability_id":"math.arctan"}}}'

Inspect the trust tier and required assurance level before execution. Pin calculation_version (1.0.7) when reproducibility matters. Full protocol notes: MCP docs.