Around your space

Orthogonality

  • (d) _l_ (d') when their angle = 90
  • if (d) _l_ (d') any line // to one is _l_ to the other
  • a st. line (d) is _l_ to plane (p) if and only if it is _l_ to 2 int st lines contained in (p)
  • 2 planes are _l_ if their angle= 90
  • through a given pt one and only one st line can be drawn _l_ to a given plane
  • if (d) _l_ to plane (p) then (d)_l_(a) any line in (p)

How to get an angle ?

  • angle of a st line and a plane : The acute angle of a plane (p) and a st line (R) is the angle HIA where h is the the orthogonal proj of any pt A of (R) on (p)

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  • Angle b/w two planes : (ADC) n (BDC) = (DC) ==> acute angle of the 2 planes is the acute angle of the 2 _l_ drawn through a pt E of (DC) in each of the two planes

What is the mediator plane ?

Mediator plane of [AB] plane _l_ to [AB] at its midpt

  • Any pt of mediator plane is equidistant from extremeties

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