A
6. In the given figure, ABCD is a quadrilateral
in which AB = AD and BC = DC. Prove that
(i) AC bisects ZA and ZC, (ii) BE = DE,
(iii) ZABC = ZADC.
B
-
D
E
C
Answers
Given : In quadrilateral ABCD , AB=AD , BC=DC
1) in triangle ABC and ADC
AB = AD (given
BC= DC (given
AC=AC ( common side
triangle ABC ~ triangle ADC ( by SSS rule
angle BAC = angle CAD ( by CPCT
also angle BCA = DCA ( by CPCT
Hence proved AC bisect angle A and C
2) in triangle ABE and ADE
AB = AD ( given
AE = AE( common side
angle A = angle A ( AC bisect angle A
triangle ABE ~ ADE ( by SAS rule
BE = DE ( by CPCT
3) in triangle ABC and ADC
angleABC=ADC ( by CPCT
Answer:
[tex](i) Consider △ ABC and △ ADC
It is given that AB = AD and BC = DC
AC is common i.e. AC = AC
By SSS congruence criterion
△ ABC ≅ △ ADC ……… (1)
∠ BAC = ∠ DAC (c. p. c. t)
So we get
∠ BAE = ∠ DAE
We know that AC bisects the ∠ BAD i.e. ∠ A
So we get
∠ BCA = ∠ DCA (c. p. c. t)
It can be written as
∠ BCE = ∠ DCE
So we know that AC bisects ∠ BCD i.e. ∠ C
(ii) Consider △ ABE and △ ADE
It is given that AB = AD
AE is common i.e. AE = AE
By SAS congruence criterion
△ ABE ≅ ∠ ADE
BE = DE (c. p. c. t)
(iii) We know that △ ABC ≅ △ ADC
Therefore, by c. p. c. t ∠ ABC = ∠ ADC.