Angle dièdre

Résumé

En géométrie, l'angle entre deux plans est appelé angle dièdre, ou angle diédral (anglicisme). L'angle dièdre d'un tétraèdre régulier, correspond à l'angle observé au sol, dans un plan perpendiculaire à l'une des arêtes au sol, que font la base du tétraèdre et une face. Face dont la base est, au sol, « vue de bout » (soit un point pour une arête). L'angle dièdre de deux plans peut être mesuré sur les « bords » des plans, c'est-à-dire suivant leur ligne d'intersection. L'angle dièdre \phi_{AB} entre deux plans dénotés A et B est l'angle entre leurs deux vecteurs normaux \mathbf{n}{A} et \mathbf{n}{B} : \cos \phi_{AB} = \mathbf{n}{A} \cdot \mathbf{n}{B} Un angle dièdre peut être signé ; par exemple, l'angle dièdre \phi_{AB} peut être défini comme l'angle de rotation (suivant leur ligne d'intersection) qui permettrait au plan A pour se superposer au plan B. Donc, \phi_{AB} = -\phi_{BA}. En particulier

Source officielle

https://fr.wikipedia.org/wiki/Angle_di%C3%A8dre

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