if the bisectors of the vertically angle of a ∆ bisects the base of the ∆ then then the ∆ is a isosceles
Answers
Step-by-step explanation:
We are given a point D on side BC of a ∆ ABC such that
∠ BAD = ∠ CAD and BD = CD
We want to prove that AB =AC.
Now we produce our line AD to E , As AD = DE , Then join CE.
according to our figure :
Now In ∆ ABD and ∆ ECD
BD = CD ( Given )
AD = ED ( By construction )
∠ ADB = ∠ EDC ( Vertically opposite angles )
Hence
∆ ABD ≅ ∆ ECD ( By SAS rule )
So,
AB = EC -------------------- ( 1 ) ( BY CPCT )
And
∠ BAD = ∠ CED -------------------- ( 2 ) ( BY CPCT )
So we get
∠ CED = ∠ CAD ( As given ∠ BAD = ∠ CAD )
So from base angle theorem we get
AC = EC
So,
AB = AC ( As we know from equation 1 , AB = EC )
Hence
In ∆ ABC , AB = AC , So ∆ ABC is a isosceles triangle . ( Hence proved )
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