ABC is an isosceles triangle in which AB=AC.AD bisects exterior angles PAC and CD parallel AB.Prove that-i)angle DAC=angle BAC ii)∆BCD is a parallelogram -Maths 9th

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Answer :

AB =AC(given) Angle ABC =angle ACB (angle opposite to equal sides) Angle PAC=Angle ABC +angle ACB (Exterior angle property) Angle PAC =2 angle ACB - - - - - - (1)    AD BISECTS ANGLE PAC. ANGLE PAC=2 ANGLE DAC--------(2) FROM EQ 1 AND 2 2ANGLE DAC=2 ANGLE ACB ANGLE DAC=ANGLE ACB THESE ANGLES ARE FORMED WHEN BC AND AD ARE LINE SEGMENT AND AC IS TRANSVERSAL BC||AD BA||CD (GIVEN ) THEREFORE ABCD IS A PARALLEGRAM. HENCE PROVED........

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