Arc length

Chapter 3 Class 11 Trigonometric Functions
Concept wise

This video is only available for Teachoo black users

Introducing your new favourite teacher - Teachoo Black, at only βΉ83 per month

### Transcript

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

Made by

#### Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths and Science at Teachoo.