Q3 of 35 Page 11

If the distance between two parallel tangents of a circle is 10cm, what is the radius of the circle?


O is the centre of circle and tangents from point A and B are parallel


We know that the line joining point of contacts of two parallel tangents (here AB) passes through the centre


And as a line from the centre is perpendicular to tangent, hence that line(AB) will be the distance between parallel tangents


AB passes through centre O hence AB is also the diameter of the circle


Hence the distance between the two parallel tangents will be the diameter of the circle


The distance AB = 10 cm in diameter of the circle


Hence radius will be half of the diameter which is 5 cm


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