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

              

Answers (1)
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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