∫BM+CN = MN,NP=CN
∴BM=MP
And ∵△ABC is an equilateral triangle, ∴ △ ABC = ∠ ACB = 60.
And BD = DC, ∠ BDC = 120, ∴ DBC = ∠ DCB = 30.
∴∠DBM=∠DCN=90
According to the point on the bisector of the angle, the distance between the feet is equal.
∵NP=CN, ∴DN is the bisector of ∠CDP, ∴ CDN = ∠ PDN.
∵BM=MP, ∴DM is the angular bisector of ∠BDP, ∴ BDM = ∠ PDM.
∠∠MDN =∠PDN+∠PDM =∠BDC/2 = 60
This is the correct answer process, I hope to adopt ~ ~ ~ remember to add points.