In the diagram shown, ABCD is a square and point F lies on BC. DEC is equilateral and EB=EF. What is the measure of EBC?
D C B A E F


Answer:

75

Step by Step Explanation:
  1. Given, ABCD is a square, DEC is an equilateral triangle and EB=EF.
    DCB=90 and DCE=60
    ECF=30
  2. Since DC=CE     [Sides of an equilateral triangle]
    and DC=CB     [Sides of a square]
    CE=CB
    ECB is an isosceles triangle.
    EBC=BEC            [
    Now, \angle ECB + \angle EBC + \angle BEC = 180^\circ \space\space\space\space\space\space\space\space\space\space\space\space [\text{ Angle Sum Property of a triangle}]
    \implies \angle EBC + \angle EBC + 30^\circ = 180^\circ
    \implies \angle EBC = \dfrac{ (180 - 30) } { 2 } = 75^\circ
  3. Given, EB = EF
    \therefore \angle BFE = \angle EBC = 75^\circ
  4. Hence, the value of \angle EBC is \angle 75^\circ.

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