Consider the quadrilateral BCEF inscribed in circle A. Diagonals EB and CF intersect at point D.
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Quadrilateral BCEF in circle A with diagonals EB and CF is given below.
Step-by-step explanation:
From the diagram, quadrilateral BCEF is a cyclic quadrilateral.
Opposite angles if a cyclic quadrilateral sum up to 180°
m∠ECB + m∠EFB=180
The diagonals intersect at D to form two pairs of vertical angles, and vertical angles are congruent
m∠CDB≅m∠EDF
Also sum of angles in triangle CBD is 180°.
m∠CDB +m∠DCB+m∠CBD =180