In a circle with centre O, AB and CD are two diameters perpendicular to each other. The length of chord AC is
Given: O is the centre of circle
AB and CD are diameters of the circle
AO = BO = CO = DO (Radius of the circle)
In right angle 
AOC,
Cos A = 
Cos A = 
Cos A = 
(i)
∠OMA = 90°
∠AOM = ∠MAO = 45°
Using value of angle A in (i)
Cos 45° = 
= 
AC = 
AB
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