QUESTION IMAGE
Question
2 in parallelogram abcd on the right, given ae and cf are the perpendicular lines drawn from vertices a and c on diagonal bd respectively, answer the questions below.
(1) draw a line segment on the right figure according to the question.
(2) prove that quadrilateral aecf formed by connecting points a with e, and points c with f respectively is a parallelogram. fill the appropriate words in the blanks.
proof
in \\( \triangle aeb \\) and \\( \triangle \square \\),
from the property of a parallelogram,
\\( \square = \square \cdots \cdots \\) ①
given: \\( \angle \square = \angle \square = 90 ^ { \circ } \cdots \cdots \\) ②
from \\( a b \parallel c d , \angle \square = \angle \square \cdots \cdots \\) ③
from ①, ②, and ③, since the \\( \square \\) and one \\( \square \\) are equal respectively,
\\( \triangle \square \cong \triangle \square \\). therefore, \\( a e = c f \\).
from \\( a e \perp b d \\) and \\( c f \perp b d , a e \parallel \square \\).
from \\( a e \parallel c f \\) and \\( a e = c f \\),
since a pair of sides are both \\( \square \\) and \\( \square \\),
quadrilateral aecf is a parallelogram.
3 in parallelogram abcd on the right, let o be the intersection point of two diagonals ac and bd. then, place two points e and f on diagonal bd, so that \\( e o = f o \\). in this case, prove that quadrilateral aecf is a parallelogram as follows. fill the appropriate words in the blanks.
proof
since point o is the intersection point of the diagonal lines of parallelogram abcd,
\\( a o = \square \cdots \cdots \\) ①
given: \\( \square = \square \cdots \cdots \\) ②
from ① and ②,
since two \\( \square \\) intersect at the \\( \square \\) of each,
quadrilateral aecf is a parallelogram.
Step1: Analyze the first proof (Problem 2)
- In \(\triangle AEB\) and \(\triangle CFD\), from the property of a parallelogram \(AB = CD\) (opposite sides of a parallelogram are equal).
- Given \(\angle AEB=\angle CFD = 90^{\circ}\) (AE and CF are perpendicular to BD).
- From \(AB\parallel CD\), \(\angle ABE=\angle CDF\) (alternate - interior angles).
- Since two angles and one side (AAS - Angle - Angle - Side) are equal respectively, \(\triangle AEB\cong\triangle CFD\).
- From \(AE\perp BD\) and \(CF\perp BD\), \(AE\parallel CF\).
- Since a pair of sides (AE and CF) are both parallel and equal, quadrilateral \(AECF\) is a parallelogram.
Step2: Analyze the second proof (Problem 3)
- Since point \(O\) is the intersection point of the diagonal lines of parallelogram \(ABCD\), \(AO = CO\) (diagonals of a parallelogram bisect each other).
- Given \(EO = FO\).
- From \(AO = CO\) and \(EO = FO\), since two diagonals (\(AC\) and \(EF\)) intersect at the mid - point of each, quadrilateral \(AECF\) is a parallelogram (a quadrilateral whose diagonals bisect each other is a parallelogram).
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For problem 2:
- First blank: \(CFD\)
- Second and third blanks: \(AB\), \(CD\)
- Fourth and fifth blanks: \(\angle AEB\), \(\angle CFD\)
- Sixth and seventh blanks: \(\angle ABE\), \(\angle CDF\)
- Eighth blank: two angles
- Ninth blank: side
- Tenth and eleventh blanks: \(AEB\), \(CFD\)
- Twelfth blank: \(CF\)
- Thirteenth and fourteenth blanks: parallel, equal
For problem 3:
- First blank: \(CO\)
- Second and third blanks: \(EO\), \(FO\)
- Fourth blank: diagonals
- Fifth blank: mid - point