Ex 10.1, 10 - Find angle between x-axis and line joining - Slope - Finding slope

  1. Chapter 10 Class 11 Straight Lines
  2. Serial order wise
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Ex10.1, 10 Find the angle between the x-axis and the line joining the points (3, โ€“1) and (4, โ€“2). First we find slope of line joining the points (3, โ€“1) and (4, โ€“2). We know that slope of line passing through (x1, y1) and (x2, y2) is m = (๐‘ฆ_2 โˆ’ ๐‘ฆ_1)/(๐‘ฅ_2 โˆ’ ๐‘ฅ_1 ) Here x1 = 3, y1 = โ€“1 & x2 = 4, y2 = โ€“2 Slope of line joining (3, โ€“1) and (4, โ€“2) is m = ( โˆ’ 2 โˆ’ ( โˆ’ 1))/(4 โˆ’ 3) = ( โˆ’ 2 + 1)/(4 โˆ’ 3) = ( โˆ’ 1)/1 = โ€“1 Now, Slope = m = tan ฮธ where ฮธ is the angle between line and positive x-axis So m = tan ฮธ โ€“1 = tan ฮธ tan ฮธ = โ€“1 tan ฮธ = tan (135ยฐ) ฮธ = 135ยฐ So, Required angle = ฮธ = 135ยฐ

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  • Dev San's image
     theta is taken in 2 quadrant as tan has negative value... can it be taken in 4 quadrant as tan is also negative in 4 quadrant also..



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  • Pulkit Singla's image
    class 11th. maths ncert. ex 10.1  . question 10 : if tan is negative in the 2nd and the 4rth quadrants , then why answer is given only for 2nd quadrant?

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