straight line

• gradient -

  $m=$$tan@$
• collinearity -

  • gradients must be equal with a common point
• perpindicular line -

  • find gradient
  • m(flip sign and fraction)xm=-1
  • sub in m
• distance formula-

  $d=$$√(x2-x1)^2+$$(y2-y1)^2$
• midpoint-

  $((x1+x2)/2,(y1+y2)/2)$
• equation of a straight line -

  $y-b=$$m(x-a)$
• perpindicular bisectors -

  • find midpoint
  • find gradient
  • flip gradient
  • straight line equation
• medians -

  • midpoint
  • gradient
  • straight line equation
• altitudes -

  • flipped gradient
  • line equation
• point of intersection, orthocentre, circumcentre and centroids use simultaneous equations