Question

plz explain in a simple way

Answer 1

Given :- AB= AC
THEREFORE, angle ABC = angle ACB
In triangle ACD
AC= AD so, angle ACD = angle ADC
In triangle BCD,
angle ABC + angle ACB + angle ACD + angle ADC = 180
2( angle ACB) + 2( angle ACD) = 180
angle ACB + angle ACD = 90
angle BCD = 90 (since, ACB + ACD).
Hence , proved
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