Respuesta :

We have an angle formed by two intersecting chords inside a circle.

So four angles are formed:

Let's use the next formula:

= 1/2(sum of intercepted arcs)

Then m∠BEC = 1/2( mAD + mBC)

Replace the values and solve

m∠BEC = 1/2(103+115)

m∠BEC = 1/2(218)

m∠BEC = 109°

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