# An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 2 Search : perpendicular
 perpendicular   پالار   pâlârFr.: perpendiculaire   A line or plane at right angles to another line or plane. Two curves are said to be perpendicular if their tangent lines are mutually perpendicular. → normal; → verticalFrom M.E. perpendiculer(e), from O.Fr. perpendiculiere, from L. perpendicularis "vertical, as a plumb line," from perpendiculum "plumb line," from perpendere "balance carefully," from per- "thoroughly" + pendere "to weigh, to hang."Pâlâr "pillar, column, main beam." perpendicular axis theorem   فربین ِ آسه‌ها‌ی ِ پالار   farbin-e âsehâ-ye pâlârFr.: théorème des axes perpendiculaires   The → moment of inertia of a plane object (→ lamina) about an axis perpendicular to the plane is equal to the sum of the moments of inertia about any two perpendicular axes in the plane. Thus if x and y axes are in the plane, Iz = Ix + Iy.→ perpendicular; → axis; → theorem.