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Example 4 - Minute hand of a watch is 1.5 cm long. How far

Example 4 - Chapter 3 Class 11 Trigonometric Functions - Part 2
Example 4 - Chapter 3 Class 11 Trigonometric Functions - Part 3


Transcript

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

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.