FA-16752 / Floating-point arithmetic / Member archive

Sine-pi reduces by one and loses alternating signs · case 02

Sine-pi reduces by one and loses alternating signs.

Member previewVariant 2 · 3 implementations · 11 checks per implementation

Case contract

Evaluate sin(pi*x) for finite x using modulo-two reduction, with exact integer zeros carrying the sign of x and exact half-integer extrema. Finite results are rendered to eleven significant decimal digits; modeled domain violations and arithmetic errors are explicit strings.

Why this case matters

An offline floating representation model isolates a reproducible arithmetic fault.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
three quarters	`"-0.70710678119"`	`"0.70710678119"`	Failed

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