Show that (1, -1) is the centre of the circle circumscribing the

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 Multiple Choice QuestionsLong Answer Type

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201. Show that (1, -1) is the centre of the circle circumscribing the triangle whose angular points are (4, 3), (-2, 3) and (6, -1).


Let the given points be P(4, 3), Q(-2, 3) and R(6, -1). Let 0(1, -1) be the centre of the circle.


Let the given points be P(4, 3), Q(-2, 3) and R(6, -1). Let 0(1, -1)
Fig. 7.25.

Then comma space space space OP space equals space square root of left parenthesis 4 minus 1 right parenthesis squared plus left curly bracket 3 minus left parenthesis negative 1 right parenthesis right curly bracket squared end root
rightwards double arrow space space space space space space space OP space equals space square root of left parenthesis 4 minus 1 right parenthesis squared plus left parenthesis 3 plus 1 right parenthesis squared end root
rightwards double arrow space space space space space space space OP space equals space square root of left parenthesis 3 right parenthesis squared plus left parenthesis 4 right parenthesis squared end root
rightwards double arrow space space space space space space space OP space equals space square root of 9 plus 16 end root equals square root of 25 equals 5 end root
space space space space space space space space space space QQ space equals space square root of left parenthesis negative 2 minus 1 right parenthesis squared plus left parenthesis 3 plus 1 right parenthesis squared end root
rightwards double arrow space space space space space space space QQ space equals square root of left parenthesis negative 3 right parenthesis squared plus left parenthesis 4 right parenthesis squared end root
rightwards double arrow space space space space space space space QQ equals square root of 9 plus 16 end root equals square root of 25 equals 5 space
and space space space space space space OR space equals space square root of left parenthesis 6 minus 1 right parenthesis squared plus left curly bracket negative 1 minus left parenthesis negative 1 right parenthesis right curly bracket squared end root space space
rightwards double arrow space space space space space space space OR space space equals space square root of left parenthesis 5 right parenthesis squared plus left parenthesis negative 1 plus 1 right parenthesis squared end root
rightwards double arrow space space space space space space space OR space space equals space square root of 25 plus 0 end root equals square root of 25 equals 5

Here, we have
OP = OQ = OR
⇒ O is equidistant from P, Q and R.
Hence ‘O’ is the centre of the circle circumscribing the triangle.

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 Multiple Choice QuestionsShort Answer Type

202. If A(2, -1), B(3, 4), C(-2, 3) and D(-3, -2) be four points in a plane, show that ABCD is a rhombus but not a square.


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203. Show that the points (7, 10), (-2, 5) and (3, -4) are the vertices of an isosceles right triangle.
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204. Show that A(-3, 2), B(-5, -5), C (2,-3) and D(4, 4) arc the vertices of a rhombus.
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205. Observe the graph given below and state whether triangle ABC is scalene, isosceles or equilateral. Justify your answer. Also find its area. 


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206. Find the values of x for which the distance between the point P(2, -3) and Q(x, 5) is 10 units. 
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207. Find a relation between x and y such thai the point P(x, y) is equidistant from the points A(2, 5) and B(-3, 7).
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208. If the distances of P (x, y) from the points A(3, 6) and B(-3, 4) are equal prove that 3x + y = 5 
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209. If the points A (4, 3) and B (x, 5) are on the circle with the centre O (2,3), find the value of x.


Fig. 7.28.
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 Multiple Choice QuestionsLong Answer Type

210. The line joining the points (1, -2) and (-3, 4) is trisected. Find the co-ordinates of the points of trisection. 
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