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Coordinate Geometry Test - 31

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Coordinate Geometry Test - 31
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  • Question 1
    1 / -0
    The point P divides the line segment joining the points $$\displaystyle A\left ( 2,1 \right )$$ and $$\displaystyle B\left ( 5,-8\right )$$ such that $$ \dfrac{AP}{AB}=\dfrac{1}{3}$$ If P lies on the line $$\displaystyle 2x+y+k=0$$
    then the value of k is-
  • Question 2
    1 / -0
    The midpoints of sides of a triangle are ($$3,4), (4,1)$$ and $$(2,0)$$. Which of the following is not the value of the coordinates of it's vertices?
  • Question 3
    1 / -0
    The area of triangle formed by $$(0, 0), (0, a)$$ and $$(b, 0)$$ is .......... .
    Solution
    The area of a triangle formed by joining the points $$(x_1, y_1)$$, $$(x_2, y_2)$$ and $$(x_3, y_3)$$ is

    $$A=\dfrac { 1 }{ 2 } \bigg| { y }_{ 1 }({ x }_{ 2 }-{ x }_{ 3 })+{ y }_{ 2 }({ x }_{ 3 }-{ x }_{ 1 })+{ y }_{ 3 }({ x }_{ 1 }-{ x }_{ 2 }) \bigg|$$

    Therefore, the area of a triangle formed by joining the points $$(0, 0)$$, $$(0, a)$$ and $$(b, 0)$$ is:

    $$A=\dfrac { 1 }{ 2 } \bigg| 0(0-b)+a(b-0)+0(0-0) \bigg| $$

         $$=\dfrac { 1 }{ 2 } \bigg| 0+ab \bigg| $$

         $$=\bigg| \dfrac { ab }{ 2 }  \bigg|$$
     
    Hence, the area of the triangle is $$\left| \dfrac { ab }{ 2 }  \right|$$  
  • Question 4
    1 / -0
    The end points of a diagonal of a parallelogram are $$(1, 3)$$ and $$(5, 7)$$, then the mid-point of the other diagonal is ..........
    Solution
    Given end points of diagonal of parallelogram $$(1,3)$$ and $$(5,7)$$
    We know that the mid point of two point $$(x_1,y_1) \ and \  (x_2,y_2)$$ are
    $$\dfrac{x_{1}+x_{2}}{2},\dfrac{y_{1}+y_{2}}{2}$$
    $$\Rightarrow \dfrac{1+5}{2},\dfrac{3+7}{2}$$
    $$\Rightarrow( 3,5)$$
  • Question 5
    1 / -0
    The midpoints of the sides of triangle $$ABC$$ are $$ (-1,-2), (6,1)$$ and $$(3,5) $$. The area of $$\displaystyle \triangle ABC$$ is ____ square units.
    Solution
    Area of triangle having vertices $$(x_1,y_1), (x_2,y_2)$$ and $$(x_3,y_3)$$ is given by
    Area $$ = \dfrac{1}{2} \times [ x_1 (y_2 - y_3) + x_2(y_3 - y_1) + x_3(y_1 - y_2) ] $$
    Area of triangle formed with midpoints
    $$\displaystyle =\frac{1}{2}\left [ -1\left ( 1-5 \right )+6\left ( 5+2 \right )+3\left ( -2-1 \right ) \right ]$$
    $$\displaystyle =\frac{37}{2}$$
    $$\displaystyle \therefore $$ Area of $$\displaystyle \Delta ABC=4\times \frac{37}{2}=74$$ square units.  
    $$[\because$$ Area of triangle formed by joining mid-points of the sides of given triangle is $$\left(\dfrac{1}{4}\right)^{th}$$ of the area of original triangle $$]$$
  • Question 6
    1 / -0
    Area of triangle whose vertices are $$(0, 0), (2, 3), (5, 8)$$ is ____ square units.
    Solution
    Area of the triangle with three vertices $$(x_1,y_1)$$, $$(x_2,y_2)$$ and $$(x_3,y_3)$$ is
    $$A=\dfrac { 1 }{ 2 } \left| { y }_{ 1 }({ x }_{ 2 }-{ x }_{ 3 })+{ y }_{ 2 }({ x }_{ 3 }-{ x }_{ 1 })+{ y }_{ 3 }({ x }_{ 1 }-{ x }_{ 2 }) \right|$$
    Therefore, the area of triangle with vertices $$(1,2)$$, $$(3,4)$$ and $$(5,6)$$ is:
    $$A=\dfrac { 1 }{ 2 } \left| 0(2-5)+3(5-0)+8(0-2) \right| =\dfrac { 1 }{ 2 } \left| 0+15-16 \right| =\dfrac { 1 }{ 2 } \left| -1 \right| =\dfrac { 1 }{ 2 }$$       
    Hence, the area of the triangle is $$\dfrac { 1 }{ 2 }$$ square units.
  • Question 7
    1 / -0
    The area of a triangle with the vertices $$(1, 2), (3, 4)$$ and $$(5, 6)$$, is ____ square units.
    Solution
    Area of the triangle with three vertices $$(x_1,y_1)$$, $$(x_2,y_2)$$ and $$(x_3,y_3)$$ is

    $$A=\dfrac { 1 }{ 2 } \left| { y }_{ 1 }({ x }_{ 2 }-{ x }_{ 3 })+{ y }_{ 2 }({ x }_{ 3 }-{ x }_{ 1 })+{ y }_{ 3 }({ x }_{ 1 }-{ x }_{ 2 }) \right|$$

    Therefore, the area of triangle with vertices $$(1,2)$$, $$(3,4)$$ and $$(5,6)$$ is:

    $$A=\dfrac { 1 }{ 2 } \left| 2(3-5)+4(5-1)+6(1-3) \right| =\dfrac { 1 }{ 2 } \left| -4+16-12 \right| =\dfrac { 1 }{ 2 } \left| 16-16 \right| =\dfrac { 1 }{ 2 } \left| 0 \right| =0$$

    Hence, the area of the triangle is $$0$$.
  • Question 8
    1 / -0
    The coordinates of the points $$P$$ which divides $$(1, 0)$$ and $$(0, 0)$$ in $$1 : 2$$ ratio are .......... .
    Solution
    We know that if a point $$P(x,y)$$ divides the line segment $$AB$$ joining the points $$A\left( { x }_{ 1 },{ y }_{ 1 } \right)  \&  B\left( { x }_{ 2 },{ y }_{ 2 } \right)$$  in the ratio $$m:n$$ then, by the section formula, we have
    $$\\ x=\dfrac { n{ x }_{ 1 }+m{ x }_{ 2 } }{ m+n }  \&  y=\dfrac { n{ y }_{ 1 }+m{ y }_{ 2 } }{ m+n } .\\$$
    Hence, $$m = 1, n = 2, A = (1, 0)$$ and $$B = (0, 0)$$
    Let $$P(x, y)$$ be the required point. 

    $$\therefore$$  $$x=\dfrac { (1\times 0)+(2\times 1) }{ 1+2 } =\dfrac { 0+2 }{ 3 } =\dfrac { 2 }{ 3 }$$
    and
        $$y=\dfrac { (1\times 0)+(2\times 0) }{ 1+2 } =\dfrac { 0+0 }{ 3 } =0$$
     
    Therefore, the coordinates of the point is $$\left( \dfrac { 2 }{ 3 } ,0 \right)$$.
  • Question 9
    1 / -0
    Find the area of $$\Delta ABC$$, in which $$A = (2, 1), B = (3, 4)$$ and $$C = (-3, -2).$$
    Solution
    Area of triangle with vertices $$(x_1,y_1)$$, $$(x_2,y_2)$$ and $$(x_3,y_3)$$ is:
    $$A=\dfrac { 1 }{ 2 } \left| x_{ 1 }(y_{ 2 }-y_{ 3 })+x_{ 2 }(y_{ 3 }-y_{ 1 })+x_{ 3 }(y_{ 1 }-y_{ 2 }) \right|$$
    Therefore, the area of triangle with vertices $$(2,1)$$, $$(3,4)$$ and $$(-3,-2)$$ is:
    $$A=\displaystyle \frac { 1 }{ 2 } \left| 2(4-(-2))+3(-2-1)-3(1-4) \right| $$
    $$=\dfrac { 1 }{ 2 } \left| 2(6)+3(-3)-3(-3) \right| $$
    $$=\dfrac { 1 }{ 2 } \left| 12-9+9 \right|$$
    $$ =\dfrac { 1 }{ 2 } \left| 12 \right| =6$$ square units.
  • Question 10
    1 / -0
    If coordinates of P,Q, and R are (3,6),(-1,3) and (2,-1) respectively. Then area of $$\displaystyle \triangle PQR$$ is ____ square units.
    Solution
    Area of triangle having vertices $$(x_1,y_1), (x_2,y_2)$$ and $$(x_3,y_3)$$ is given by
    $$ = \dfrac{1}{2} \times [ x_1 (y_2 - y_3) + x_2(y_3 - y_1) + x_3(y_1 - y_2) ] $$
    Area of $$\displaystyle \Delta PQR$$ is given by
    $$\displaystyle =\frac{1}{2}\left [ 3\left ( 3+1 \right )-1\left ( -1-6 \right )+2\left ( 6-3 \right ) \right ]$$
    $$\displaystyle =\frac{1}{2}\left ( 12+7+6 \right )=12.5$$ square units.
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