Results 1 to 2 of 2

Math Help - AS Level Maths question.

  1. #1
    Newbie
    Joined
    Oct 2010
    Posts
    1

    AS Level Maths question.

    Question:
    A(7,2) and C(1,4) are two vertices of a square ABCD.
    a) Find in the form ax +by=c the equation of the diagonal BD.
    b) Find the coordinates of B and of D.

    I have done part a) and got the answer 3x-y=9
    but i don't know how to do part b)
    please help!
    thanks x
    Last edited by mr fantastic; October 15th 2010 at 12:49 PM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    A riddle wrapped in an enigma
    masters's Avatar
    Joined
    Jan 2008
    From
    Big Stone Gap, Virginia
    Posts
    2,551
    Thanks
    12
    Awards
    1
    Quote Originally Posted by caramel17 View Post
    Question:
    A(7,2) and C(1,4) are two vertices of a square ABCD.
    a) Find in the form ax +by=c the equation of the diagonal BD.
    b) Find the coordinates of B and of D.

    I have done part a) and got the answer 3x-y=9
    but i don't know how to do part b)
    please help!
    thanks x

    Hi Caramel17,

    You know the midpoint of AC is (4, 3). Let's call that point M.

    You found the slope of the perpendicular which passes through
    points B and D.

    That would be 3.

    Using the slope of 3 and the midpoint M(4, 3) and an endpoint B(x, y), we get:

    \dfrac{3-y}{4-x}=\dfrac{3}{1}

    Equating the numerators and denominators, we arrive at:

    4-x=1  \: \text{and} \:3-y=3

    x=3 \:\:\text{and}\:\:y=0

    \boxed{B(x, y) = B(3, 0)}

    You can find the coordinates of D in a similar fashion.

    Let coordinates of D be (x_1, y_1)

    \dfrac{y_1-3}{x_1-4}=\dfrac{3}{1}

    x_1-4=1  \: \text{and}\:y_1-3=3

    x_1=5 \:\text{and}\:y_1=6

    \boxed{D(x_1, y_1) = D(5,6)}




    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. (UK) A-level Maths H/W.
    Posted in the Math Topics Forum
    Replies: 4
    Last Post: October 19th 2007, 12:06 PM
  2. A level maths 06
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: May 24th 2007, 02:04 PM
  3. A level Maths
    Posted in the Pre-Calculus Forum
    Replies: 12
    Last Post: May 23rd 2007, 11:22 AM
  4. GCSE A Level Maths Qns
    Posted in the Calculus Forum
    Replies: 2
    Last Post: May 21st 2006, 05:58 AM
  5. A Level Maths Revision
    Posted in the Math Forum
    Replies: 1
    Last Post: May 5th 2006, 12:26 AM

Search Tags


/mathhelpforum @mathhelpforum