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Zorluk: OrtaProperties of Quadrilaterals

In rectangle ABCDABCD, diagonals ACAC and BDBD intersect at point EE. If the measure of ∠AEB\angle AEB is 120∘120^\circ and AC=16AC = 16, what is the length of side BCBC?

Cevap: 8

Cevap

The length of side BCBC is 88.
In any rectangle, the diagonals are congruent and bisect each other. Given AC=16AC = 16, the distance from the intersection point EE to any vertex is 88, so BE=EC=8BE = EC = 8. Because ∠AEB\angle AEB and ∠BEC\angle BEC lie along the straight diagonal line ACAC, they are supplementary, giving ∠BEC=180∘−120∘=60∘\angle BEC = 180^\circ - 120^\circ = 60^\circ. Triangle BECBEC is an isosceles triangle with BE=EC=8BE = EC = 8 and a vertex angle of 60∘60^\circ, which forces it to be equilateral. Consequently, all sides of △BEC\triangle BEC are equal, so BC=8BC = 8.

Adım Adım Çözüm

1
Calculate the lengths of the diagonal segments from the center point EE.
BE=EC=8BE = EC = 8
The diagonals of a rectangle are congruent and bisect each other, so each half-diagonal equals half of ACAC.
2
Determine the measure of adjacent angle ∠BEC\angle BEC.
∠BEC=60∘\angle BEC = 60^\circ
Angles ∠AEB\angle AEB and ∠BEC\angle BEC form a straight line (linear pair), so their sum is 180∘180^\circ.
3
Analyze △BEC\triangle BEC to find the length of side BCBC.
BC=8BC = 8
An isosceles triangle with a 60∘60^\circ vertex angle has base angles of 60∘60^\circ as well, making it an equilateral triangle where all sides are equal to 88.

Anahtar Kavram

Diagonals of a rectangle are equal in length and bisect each other, dividing the rectangle into two pairs of congruent isosceles triangles.
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