Example 4 - Chapter 3 Class 11 Trigonometric Functions

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 1 hour So, Degree completed in 1 minute = 𝟑𝟔𝟎/𝟔𝟎° Degree completed in 40 minute = 360/60 × 40° = 240° Converting degree into radians θ = 240° = 240° × 𝝅/(𝟏𝟖𝟎°) = 𝟒𝝅/𝟑 Putting values in formula θ "= " 𝑙/𝑟 " " 𝒍 = r θ = 1.5 × 𝟒𝝅/𝟑 = 0.5 × 4𝜋 = 2𝝅 = 2 × 3.14 = 6.28 cm