# 4. In Fig 7.25,$\overline{AB}$ and $\overline{CD}$ bisect each other at $O$. (i) State the three pairs of equal parts in two triangles $AOC$ and $BOD$. (ii) Which of the following statements are true?                 $(a) \bigtriangleup AOC\cong \bigtriangleup DOB$                  $(b) \bigtriangleup AOC\cong \bigtriangleup BOD$

P Pankaj Sanodiya

i) The three pairs of equal parts in two triangles $AOC$ and $BOD$ are:

CO = DO (given)

OA = OB (given )

$\angle COA = \angle DOB$ ( As opposite angles are equal when two lines intersect.)

ii) So by SAS congruency rule,

$\Delta COA \cong\Delta DOB$

that is

$\bigtriangleup AOC\cong \bigtriangleup BOD$

Hence, option B is correct.

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