Straight Line

• What is the formula for the gradient between two points?


  m = y2 - y1/x2 - x1
• What is the general formula for the equation of a straight line?


  y-b = m(x-a)
• How do you find the gradient of a line if you only know its equation?


  1. Rearrange to make y the subject of the equation
  2. The gradient is the co-efficient of x
• What is the formula linking the gradient to the angle that a line makes with the x axis?


  m = tanx
• What is the rule for the gradients of parallel lines?


  They are the same
• What do perpendicular gradients multiply to give?


  -1
• What two things do you do to find a perpendicular gradient?


  1. Flip it upside down
  2. Change the sign
• What is the distance formula?


  $squareroot (x2-x1)^2+$$(y2-y1)^2$
• What are the two properties of the perpendicular bisector of a line?


  1. It goes through the midpoint of the line
  2. It is perpendicular to the line
• What are the two properties of the median of a traingle through point A?


  1. It goes through point A
  2. It goes through the midpoint of the opposite side
• What are the two properties of the altitude of a traingle through point A?


  1. It goes through point A
  2. It is perpendicular to the opposite side
• How do you find the gradient of an altitude of a traingle through point A?


  1. Find the gradient of the side opposite A
  2. Flip and change sign
• How do you find the gradient of a median of a traingle through point A?


  1. Find the midpoint of the side opposite A
  2. Find the gradient from the midpoint to A
• What is the gradient of a horizontal line?


  0
• What is the gradient of a verticle line? 


  undefined
• What is the equation of a horizontal line? 


  y = b
• What is the equation of a verticle line? 


  x = a