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  1. Chapter 10 Class 11 Straight Lines
  2. Serial order wise

Transcript

Ex 10.1, 10 Find the angle between the x-axis and the line joining the points (3, –1) and (4, –2). First we find slope of line joining the points (3, –1) and (4, –2). We know that slope of line passing through (x1, y1) and (x2, y2) is m = (𝑦_2 βˆ’ 𝑦_1)/(π‘₯_2 βˆ’ π‘₯_1 ) Here x1 = 3, y1 = –1 & x2 = 4, y2 = –2 Slope of line joining (3, –1) and (4, –2) is m = ( βˆ’2 βˆ’ (βˆ’1))/(4 βˆ’ 3) = ( βˆ’ 2 + 1)/(4 βˆ’ 3) = ( βˆ’ 1)/1 = –1 Ex 10.1, 10 Find the angle between the x-axis and the line joining the points (3, –1) and (4, –2). First we find slope of line joining the points (3, –1) and (4, –2). We know that slope of line passing through (x1, y1) and (x2, y2) is m = (𝑦_2 βˆ’ 𝑦_1)/(π‘₯_2 βˆ’ π‘₯_1 ) Here x1 = 3, y1 = –1 & x2 = 4, y2 = –2 Slope of line joining (3, –1) and (4, –2) is m = ( βˆ’2 βˆ’ (βˆ’1))/(4 βˆ’ 3) = ( βˆ’ 2 + 1)/(4 βˆ’ 3) = ( βˆ’ 1)/1 = –1 = ( βˆ’2 + 1)/(4 βˆ’ 3) = ( βˆ’1)/1 = –1 Now, Finding Angle from Slope Now, Slope = m = tan ΞΈ where ΞΈ is the angle between line and positive x-axis So, m = tan ΞΈ –1 = tan ΞΈ tan ΞΈ = –1 tan ΞΈ = tan (135Β°) ΞΈ = 135Β° So, Required angle = ΞΈ = 135Β° Rough Ignoring signs tan ΞΈ = 1 So, ΞΈ = 45Β° As tan is negative ∴ ΞΈ will lie in 2nd quadrant, So, ΞΈ = 180Β° – 45Β° = 135Β°

About the Author

Davneet Singh's photo - Teacher, Computer Engineer, Marketer
Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.