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Canonical Key
z*cosh(z)
Closed Form
f(z) = z*cosh(z)

Image domain \(f(\mathbb{D})\)

The image of the unit disk under \(f\): concentric circles \(|z|=r\) and radial spokes mapped through \(f(z)=z+a_2z^2+\dots\); the bold curve is the boundary \(f(e^{i\theta})\). Rendered in your browser from the certified Taylor coefficients - nothing is computed server-side.

Taylor series
r* ≈ 0.800
Radius of starlikeness r* ≈ 0.8000
disproven f is starlike on |z| < r*; the colored disk shows the certified region.

Unit disk explorer - hover to evaluate

Hover over the disk

Related

Univalence Criteria

Schwarzian norm ||S(f)||
1.533
✓ Nehari ≤ 2 → univalent (proven)
Pre-Schwarzian norm ||T(f)||
0.868
✓ Becker ≤ 1 → univalent (proven)

Facts (8)

Property Kind Params Holds Value / r Status Confidence
B membership {} 0.8677 ✓ proven rigorous_verified
K membership {} -6.1778 unscreened -
N membership {} 1.5328 ✓ proven rigorous_verified
||T(f)|| bound {} 0.8677 ✓ proven rigorous_verified
r* radius {} - r ≤ 0.865 🔬 screened numerical_strong
||S(f)|| bound {} 1.5328 ✓ proven rigorous_verified
S* membership {} r ≤ 0.800 ✗ disproven proven
S membership {} - unscreened -

Verification Runs (4)

Verifier Property Direction Outcome Domain r Witness Engine
boundary_scan_closed_form_v31 starlike disproves pass 0.800 0.9*exp(i*1.546253) boundary_v3.1
pointwise_starlike_iv starlike disproves pass 0.990 [6.062001655779399e-17, 0.99] gft-0.1.0-reaudit-20260610
boundary_scan_centered_v31 starlike disproves pass 0.800 0.9*exp(i*1.59534) boundary_v3.1
boundary_scan_closed_form starlike disproves pass 0.800 0.9*exp(i*1.546253) boundary_v3.0

Instances (1)

{}
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