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- Anurag@Gurome
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(1) Angle A = 40º
Let the point of intersection of CD and BE be I.
So angle BIC = 90 + (40/2) = 110 = angle DIE.
So, (x + y) = 360 - (110 + 40) = 210; SUFFICIENT.
(2) Angle ABC = Angle ACB implies ABC is an isosceles triangle. But again we are not able to find the values of x and y; NOT sufficient.
The correct answer is A.
Last edited by Anurag@Gurome on Fri Feb 03, 2012 11:37 pm, edited 1 time in total.
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Only A is sufficient to deduct that X+Y is 210. We don't need individual values for X & Y.
40 + B + C =180
B+C = 140 ==> (B+C)/2 = 70
Let the point of intersection be O.
Angle BOC = 180 ; BOD = 70 ; COE = 70 ; DOE = 110
110 - C/2 = 180 - Y (eq 1)
110- B/2 = 180 - X
i.e 220-70=360-(X+Y)
X+Y = 210.
A Sufficient
40 + B + C =180
B+C = 140 ==> (B+C)/2 = 70
Let the point of intersection be O.
Angle BOC = 180 ; BOD = 70 ; COE = 70 ; DOE = 110
110 - C/2 = 180 - Y (eq 1)
110- B/2 = 180 - X
i.e 220-70=360-(X+Y)
X+Y = 210.
A Sufficient
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What is the OA?
A seems right.
as we see that BE & CD is bisectors of angle ABC & angle ACB respectively.
so from stat 1), we know that angle BAC = 40
so, angle ABC + angle ACB = 140
so, (angle ABC + angle ACB)/2 = (angle EBC + angle DCB) = 70
so angle BOC = 110 (sum of angles of a triangle is 180)
SO, angle DOE = 110
we know that angle BAC = 40
as the sum of angles of a quadrilateral is 360
so (x+y) = 360 - (angle DOE + angle DAE)
= 210
What is the OA?
A seems right.
as we see that BE & CD is bisectors of angle ABC & angle ACB respectively.
so from stat 1), we know that angle BAC = 40
so, angle ABC + angle ACB = 140
so, (angle ABC + angle ACB)/2 = (angle EBC + angle DCB) = 70
so angle BOC = 110 (sum of angles of a triangle is 180)
SO, angle DOE = 110
we know that angle BAC = 40
as the sum of angles of a quadrilateral is 360
so (x+y) = 360 - (angle DOE + angle DAE)
= 210
- ronnie1985
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Please give the proof that the opposite angle formed by angle bisectors with the third vertex is 90 + half angle of vertexAnurag@Gurome wrote:(1) Angle A = 40º
Let the point of intersection of CD and BE be I.
So angle BIC = 90 + (40/2) = 110 = angle DIE.
So, (x + y) = 360 - (110 + 40) = 210; SUFFICIENT.
(2) Angle ABC = Angle ACB implies ABC is an isosceles triangle. But again we are not able to find the values of x and y; NOT sufficient.
The correct answer is A.
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- ronnie1985
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Please provide proof for the theorems used in solving this question
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