Perpendicular from the Center to a Chord Bisects the Chord
In circle of ...
Question
In circle of radius 5cm,AB and AC are the two chords such that AB=AC=6cm. Find the length of chord BC.
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Solution
AD is the bisector of ∠BAC and perpendicular bisector of BC passing through centre O. ¯¯¯¯¯¯¯¯¯AD and ¯¯¯¯¯¯¯¯BC at midpoint M. ∴¯¯¯¯¯¯¯¯¯¯BM=¯¯¯¯¯¯¯¯¯¯CM In right angled triangle, △AMC MC2=AC2−AM2=36−AM2 In right angled triangle, △OMC MC2=OC2−OM2 =25−(AO−OM)2=25−(5−AM)2 ∴36−AM2=25−(5−AM)2 or AM=3.6cm ¯¯¯¯¯¯¯¯¯¯MC=√36−(3.6)2 =√23.044.8cm ∵BC=2MC ∴BC=2×4.8=9.8cm