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AD is both the median and the altitude from A to BC in triangle ABC.
Which congruence of triangles ABD and ACD (right angle at D, BD=DC, AD common) proves AB = AC?

Class 9Criteria for CongruenceGeometry — Triangles
  • ASAS
  • BASA
  • CAAA
  • DSSA

Step-by-Step Solution

BD = DC (median), angle ADB = angle ADC = 90 deg (altitude, included), AD = AD common => SAS, hence AB=AC by CPCT.
Answer: A) SAS

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