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NCERT Class XI Mathematics - Trigonometric Functions - Solutions

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Question : 7 of 61
Marks: +1, -0
Find the angle in radian through which a pendulum swings if its length is 75 cm and the tip describes an arc of length
(i) 10 cm (ii) 15 cm (iii) 21 cm
Solution:  
(i) r = 75 cm, l = 10 cm ⇒ θ = lr\frac{l}{r} = 1075\frac{10}{75} = 215\frac{2}{15} radians
(ii) l = 15 cm, r = 75 cm ⇒ θ = lr\frac{l}{r} = 1575\frac{15}{75} = 15\frac{1}{5} radians
(iii) l = 21 cm, r = 75 cm ⇒ θ = lr\frac{l}{r} = 2175\frac{21}{75} = 725\frac{7}{25} radians
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