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Coordinate Geometry Test - 19

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Coordinate Geometry Test - 19
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  • Question 1
    1 / -0
    Which statement is true?
    Solution
    i) The x-axis ,a line parallel to it is called horizontal line
    ii) The point (-2,3) lies in II Quadrant 
    iii) Origin is the point of intersecting of x-axis and y-axis
    iv) The point (-3,-4) lies in III quadrant .
  • Question 2
    1 / -0
    Given three vertices of a triangle whose coordinates are A (1, 1), B (3, -3) and (5, -3). Find the area of the triangle.
    Solution
    We know that the area of the triangle whose vertices are $$\displaystyle (x_{1},y_{1}),(x_{2},y_{2}),$$ and $$(x_{3},y_{3})$$ is $$\cfrac{1}{2}\left | x_{1}(y_{2}-y_{3})+x_{2}(y_{3}-y_{1}) +x_{3}(y_{1}-y_{2})\right |$$
    The three vertices of the triangle are $$A(1,1), B(3,-3), C(5,-3)$$
    Area of triangle $$=\dfrac{|1(-3-(-3)+3(-3-1)+5(1-(-3))|}{2}$$
    $$=\dfrac{|1(0)+3(-4)+4(4)|}{2}$$
    $$=\dfrac{|-12+20|}{2}$$
    $$=\dfrac{8}{2}$$
    $$=4$$ square units.

  • Question 3
    1 / -0
    The area of triangle whose vertices are $$A (-3, -1), B(5, 3)$$ and $$C(2, -8)$$ is ____ $$\text{ sq. units}$$.
    Solution
    We know that the area of the triangle whose vertices are $$\displaystyle (x_{1},y_{1}),(x_{2},y_{2}),$$ and $$(x_{3},y_{3})$$ is $$\cfrac{1}{2}\left | x_{1}(y_{2}-y_{3})+x_{2}(y_{3}-y_{1}) +x_{3}(y_{1}-y_{2})\right |$$

    The given vertices of the triangle are $$A(-3,-1), B(5,3)$$ and $$C(2,-8)$$.
    So, by using the above formula,
    $$\begin{aligned}{}\text{Area of the triangle} &= \frac{1}{2} {[ - 3(3 - ( - 8)) + 5( - 8 - ( - 1)) + 2( - 1 - 3)]}\\ &= \frac{1}{2}{[ - 33 - 35 - 8]}\\ &= \frac{{[ - 76]}}{2}\\& = \frac{{76}}{2}\quad\quad\quad\quad\dots[\text{Area can never be negative so, we ignore negative sign}]\\& = 38\text{ sq. units}\end{aligned}$$

    So, the area of the triangle is equal to $$38\text{ sq. units}$$.
  • Question 4
    1 / -0
    Refer to the following graph, and find the co-ordinates of $$N$$, which is the midpoint of $$\displaystyle \overline { AB } $$.

    Solution
    Mid-point $$=\left (\dfrac{x_1+x_2}{2},\dfrac{y_1+y_2}{2}\right)$$
    Here $$x_1=-3,x_2=6$$ and $$y_1=0,y_2=k$$
    Mid-point $$=\left (\dfrac{-3+6}{2},\dfrac{0+k}{2}\right)$$
    $$\Rightarrow\left  (\dfrac{3}{2},\dfrac{k}{2}\right)$$
  • Question 5
    1 / -0
    Given the points $$A(-1,3)$$ and $$B(4,9)$$.Find the co-ordinates of the mid-point of $$AB$$
    Solution
    $$A=(-1,3)$$ and $$B=(4,9)$$
    Here, $$x_1=-1,\,y_1=3,\,x_2=4$$ and $$y_2=9$$
    Co-ordinates of the mid-point of $$AB=\left(\dfrac{x_1+x_2}{2},\dfrac{y_1+y_2}{2}\right)$$

                                                                   $$=\left(\dfrac{-1+4}{2},\dfrac{3+9}{2}\right)$$

                                                                   $$=\left(\dfrac{3}{2},\dfrac{12}{2}\right)$$

                                                                   $$=\left(\dfrac{3}{2},6\right)$$
  • Question 6
    1 / -0
    $$M(2, 6)$$ is the midpoint of $$\overline {AB}$$. If $$A$$ has coordinates $$(10, 12)$$, the coordinates of $$B$$ are
    Solution
    Mid point $$=$$ $$\dfrac{x_1+x_2}{2}, \dfrac{y_1+y_2}{2}$$
    Here mid-point $$=(2,6)$$
    $$x_1=10,y_1=12$$
    $$\Rightarrow (2,6)=\dfrac{10+x_2}{2},\dfrac{12+y_2}{2}$$
    $$\Rightarrow \dfrac{10+x_2}{2}=2; \dfrac{12+y_2}{2}=6$$
    $$\Rightarrow x_2=4-10;y_2=12-12$$
    $$\Rightarrow x_2=-6,y_2=0$$
    $$\therefore $$ co-ordinates of $$B=(-6,0)$$.
  • Question 7
    1 / -0
    The area of the triangle formed by three vertices $$O(0, 0), A(1, 0), B(0, 1)$$ is _____ sq. units.
    Solution
    Points are given as $$O(0,0), A(1,0), B(0,1)$$. 
    When plotted on the cartesian plane, these points make a right angled triangle $$OAB$$ with
    $$OA=1$$,  $$OB=1$$
    Area of this right angled triangle $$=\dfrac12\times OA\times OB$$
                                                           $$=\cfrac12\times1\times1\ sq.unit$$
                                                           $$=\cfrac12\ sq.unit$$ 

  • Question 8
    1 / -0
    If the mid-point between the points $$(a+ b, a- b)$$ and $$(-a, b)$$ lies on the line $$ax + by = k$$, what is $$k$$ equal to?
    Solution
    Mid-point of points $$(x_1,y_1)$$ and $$(x_2, y_2)$$ is $$\bigg( \dfrac{x_1+x_2}{2}, \dfrac{y_1+y_2}{2} \bigg)$$

    Hence, mid-point of $$(a+b,a-b),(-a,b)$$ is $$\left( \dfrac { a+b-a }{ 2 } ,\dfrac { a-b+b }{ 2 }  \right) $$

                                                                             $$=\left(\dfrac { b }{ 2 } ,\dfrac { a }{ 2 } \right)$$

    Given: Mid-point lies on line $$ax+by=k$$

    $$\Rightarrow a\times \dfrac{b}{2}+b\times \dfrac{a}{2}=k$$

    $$\Rightarrow ab=k$$
  • Question 9
    1 / -0
    If O(0, 0) and P(-8, 0) then co-ordinates of its midpoint are .............
    Solution
    Let $$A(x, y)$$ be the midpoint of line segment joining points $$O$$ and $$P$$.
    By midpoint formula we can say that,
    $$(x, y) = \left( \dfrac{0 + (-8) }{2}, \dfrac{0 - 0}{2} \right ) = (-4, 0)$$
    Hence, the coordinates of midpoint is $$(-4, 0)$$
  • Question 10
    1 / -0
    The points A(5, 2), B(3, 4) and C(x, y) are collinear points and AB = BC then find the co-ordinates of C.
    Solution
    If three points $$P(x_1,y_1), Q, R(x_2,y_2)$$ are collinear.

    $$\Rightarrow PQ = QR$$ and $$Q$$ is the midpoint of $$PR$$

    The mid point $$Q = \left (\dfrac{x_1+x_2}{2}, \dfrac{y_1+y_2}{2}\right)$$

    Given, the points $$A(5, 2), B(3, 4)$$ and $$C(x, y)$$ are collinear and $$AB=BC$$ 
    $$\Rightarrow $$ $$B$$ is the mid-point of $$AC$$.
    Using midpoint formula, 
         $$\left( \dfrac{x + 5}{2} , \dfrac{y + 2}{2} \right ) = (3, 4)$$

    $$\implies \dfrac{x + 5}{2} = 3$$ and $$\dfrac{y + 2}{2} = 4$$

    $$\implies x + 5 = 6$$ and $$y + 2 = 8$$

    $$\implies x = 1$$ and $$y = 6$$
    Hence, the coordinates of $$C$$ are $$(1,6)$$.
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