If in a circle of radius r arc length of l subtend θ radian angle at centre then
Dec 10, 2021, 16:45 IST
If in a circle of radius r arc length of l subtend θ radian angle at centre then
Example 1 :-The minute hand of a watch is 1.5 cm long. How far does its move in 40 minutes? (Use π = 3.14).
Solution :-
In 60 minutes, the minute hand of a watch completes one revolution. Therefore, in 40 minutes, the minute hand turns through 2/3 of a revolution. Therefore,
radian. Hence, the required distance travelled is given by 
Example 2 :-If the arcs of the same length in two circles subtend angles 65° and 110° at the centre, find the ratio of their radii.
Solution :-
Let r1 and r2 be the radii of the two circles. Given that 
Let l be the length of each of the arc. Then 
which gives 
r1 : r2 = 22 : 13.
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