two concentric circles are radii 5cm and 3cm . find the lenght of the chord of the larger circle which touches the smaller circle
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draw a perpendicular from centre of a circle to chord
name it B
chord AC So, AB=BC
So,triangle AOB applying Pythagoras theorem
AB^2=OA^2- OB^2
=(radii of bigger circle)^2 -(radii of smaller circle)^2
=5^2-3^2
=25-9
=16
AB=4
AC=AB+BC
BC=AB
AC=4+4=8
AC=8cm
name it B
chord AC So, AB=BC
So,triangle AOB applying Pythagoras theorem
AB^2=OA^2- OB^2
=(radii of bigger circle)^2 -(radii of smaller circle)^2
=5^2-3^2
=25-9
=16
AB=4
AC=AB+BC
BC=AB
AC=4+4=8
AC=8cm
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