Three vertices of a parallelogram ABCD taken in order are A(3, 6), B(5, 10) and C(3, 2), Find (i) the coordinate of the fourth vertex D (ii) length of diagonal BD (iii) equation of the side AB of the parallelogram ABCD
Three vertices of a parallelogram taken in order are A(3, 6), B(5, 10) and C(3, 2)
(i) We need to find the coordinates of D.
We know that the diagonals of a parallelogram bisect each other.
Let (x,y) be the coordinates of D.
Therefore, Mid-point of diagonal AC = = (3,4)
And, mid-point of diagonal BD =
Thus we have
= 3 and = 4
Therefore, 5 + x = 6 and 10 + y = 8
x = 1 and y = -2
Therefore, D = (1, -2)
(ii) Length of diagonal BD =
=
=
=
=
(iii) A(3, 6) = (x1 , y1) and B(5,10) = (x2 , y2)
Slope of line AB = m =
Therefore , Equation of line AB is given by,
y - y1 = m(x - x1)
y - 6 = 2(x - 3)
y - 6 = 2x - 6
2x - y = 0
2x = y
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(a) Use a graph paper for this question taking 1 cm = 1 unit along both the x and y axis :
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(iii) Write the coordinates of B’, C’, D’ and E’.
(iv) Name the figure formed by B C D E E’ D’ C’ B’.
(v) Name a line of symmetry for the figure formed.
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(ii) Find the length of AB and AC.
(iii) Find the ratio in which Q divides AC.
(iv) Find the equation of the line AC.
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