Answers

  • qais
  • Content Quality
2016-02-20T14:37:54+05:30
See,in ΔABC
 AB = AC
⇒∠ACB = ∠ABC ( opp. angles of equal sides)
also,in ΔACD
AC= AD
∵AB = AD
so, ∠ADC = ∠ACD ( opp. angles of equal sides)
in ΔBCD
∠ABC + ∠ACB +∠ACD + ∠ADC = 180° ( sum of all angles in a triangle)
∵∠ACB +∠ACD  = ∠BCD
⇒2∠ACB =  ∠BCD
4∠ACB = 180°
⇒∠ACB = 45°
⇒2∠ACB  = 90°
∠BCD = 90° (proved )


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