straight lines

• distance formula


  √(x2-x1)² + (y2-y1)²
• perpendicular proof


  “as m1 x m⊥ = -1”
• perpendicular bisector


  -midpoint

  -gradient

  -perpendicular gradient

  -equation
• equation of altitude 


  -gradient

  -perpendicular gradient

  -equation
• equation of median


  -midpoint

  -gradient

  -equation