Coordinate geometry

**Ilsa** · October 19th 2010, 06:44 AM

Three points have coordinates o(0,0), A(5,0) and B(7,6). If P is the point (x,y) where y>0, calculate the value of x and y given that AP=BP and that the area of the triangle AOP is 10sq. units.

**Soroban** · October 19th 2010, 07:37 AM

Hello, Ilsa!

Three points have coordinates: . $O(0,0),\: A(5,0),\:B(7,6)$

If $\,P(x,y)$ where $y>0$ , calculate the value of $\,x$ and. $\,y$

given that $AP=BP$ and that the area of $\Delta AOP =10 \text{ units}&^2$

Code:

        |             (x,y)           (7,6) 
        |             P o               * B
        |                  o        *  *
        |                     o *     *
        |                   *    o   *        
        |               *           o
        |           *              *   o
        |       *                 *       o
        |   *                    *
    - - * - - - - - - - - - - - * - - - - - -
      (0,0)                   (5,0)
        O                       A

Since $\,P$ is equidistant from $\,A$ and $\,B$
. . $\,P$ lies on the perpendicular bisector of $\,AB,$
. . which has the equation: . $y \:=\:-\frac{1}{3}x + 5$

Code:

        |               P 
        |               o (x,y)
        |             * :*
        |           *   : *
        |         *     :  *        
        |       *       :y  *
        |     *         :    *
        |   *           :     *
       O| *             :      * A
    - - * - - - - - - - + - - - * - -
      (0,0)                   (5,0)

The area of $\Delta AOP$ is 10 units $^2.$

Its base is 5 and its height is $\,y$ .
. . $A \,=\,\frac{1}{2}bh \quad\Rightarrow\quad \frac{1}{2}(5)y \:=\:10 \quad\Rightarrow\quad y \,=\,4$

Hence: . $-\frac{1}{3}x + 5 \:=\:4 \quad\Rightarrow\quad x \,=\,3$

Therefore: . $P(3,\,4)$

**Ilsa** · October 19th 2010, 07:49 AM

Thanku!
It helped clear up my concepts a lot!

Thread: Coordinate geometry

LinkBack

Thread Tools

Display