ABCD is a parallelogram. If the diagonal AC bisects ∠A, then prove that:
(i) AC bisects ∠C
(ii) ABCD is a rhombus
(iii) AC ⊥ BD.
[3 Marks]
Proof:
(i) As AB || CD, we have [Opposite sides of a || gm]
∠DCA = ∠CAB
Similarly, ∠DAC = ∠DCB
But, ∠CAB = ∠DAC [Since, AC bisects ∠A]
Hence,
∠DCA = ∠ACB and AC bisects ∠C.
[1 Mark]
(ii) As AC bisects ∠A and ∠C
And, ∠A = ∠C
Hence, ABCD is a rhombus.
[1 Mark]
(iii) Since, AC and BD are the diagonals of a rhombus and
AC and BD bisect each other at right angles
Hence, AC ⊥ BD
[1 Mark]