Respuesta :

mhanifa

Answer:

  • 57°

Step-by-step explanation:

Vertical angles theorem states that vertical angles are congruent.

Arcs EF and are intercepted by vertical angles, therefore:

  • mAB = mEF = 36°

Angle addition postulate.

  • mABD = mAB + mBD

Central angle has same measure with intercepted arc.

  • mBD = m∠BCD = 21°

So the arc ABD is:

  • mABD = 36° + 21° = 57°