Question

Please help........................

Answer 1

m∠ABD = 20°

Explanation:

If m∠ABC = 40° and BD is the bisector of ∠ABC, then

(1) m∠ABD = m∠DBC

(2) m∠ABC = m∠ABD + m∠DBC

From (1) and (2) we have:

m∠ABC = 2m∠ABD

Therefore

2m∠ABD = 40° divide both sides by 2

m∠ABD = 20°