The Twist

Why the mixed derivative bends a bowl into a saddle
Bend in x  A 0.0
Bend in y  C 0.0
Twist  B 0.0
AC − B² = 0.00
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The Twist

A ten-scene, narrated walk through the mixed derivative fxy — what it means, why it twists a surface, and why it fights the bending in AC − B².

Narration plays automatically. You can pause, skip, or orbit the scene at any time.