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Arc length
Last updated at Feb. 12, 2020 by Teachoo
Example 4 The minute hand of a watch is 1.5 cm long. How far does its tip move in 40 minutes? (Use Ο = 3.14). We know that π = r ΞΈ Here, r = minute hand of clock = 1.5 cm Finding Angle π Now we know that Minute hand make 1 revolution in 1 hour Hence we can say that, Minute hand completes 360Β° in one hour In π = π/π , ΞΈ is in radians So, Degree completed in 1 minute = 360/60 Degree completed in 40 minute = 360/60 Γ 40Β° = 240Β° Hence ΞΈ = 240Β° = 240Β° Γ π/(180Β°) = 4π/3 Now Putting values in formula π = r ΞΈ (Radian measure = π/180 Γ Degree measure ) = 1.5 Γ 4π/3 = 0.5 Γ 4π = 2π = 2 Γ 3.14 = 6.28 cm