If two equal chords of a circle intersect each other, then prove that ordered parts of one chord are respectively equal to the corresponding parts of other chord.
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Solution
Given : Let on a circle C(O,r) two equal chords AB and CD intersect each other at point P. To Prove : AP=CP and PB=PD Construction : Draw OL⊥AB and OM⊥CD and join OP Proof : OL⊥AB and OM⊥CD OL=OM …..(i) [∵AB=CD] (Equal chords are (RBSESolutions.com) equidistant from center) In right angled ΔOLP and ΔOMP OL=OM [from eqn (i)] ∠OLP=∠OMP [each 900] OP=OP [common side] ∴ΔOLP=ΔOMP LP=PM …..(ii) But AB=CD 12AB=12CD AL=CM ……(iii) Adding equations (ii) and (iii) LP+AL=PM+CM AP=PC ……(iv) thus AB=CD....(v) AP=CP) Now subtracting equation (iv) from (v) AB–AP=CD–CP PB=PD