Q3 of 59 Page 178

Find the angle between the lines y = ( 2 - root 3 ) (x+5) and y = ( 2 + root 3 ) (x-7).

Given equations are:-

y = (2 - √3)(x + 5)


y = (2 - √3)x + (2 - √3)5 …(i)


and y = (2 + √3)(x – 7)


y = (2 + √3)x – 7(2 + √3) …(ii)


Now, we have to find the slope of eq. (i)


Since, the eq. (i) is in y = mx + b form, we can easily see that the slope (m1) is (2 - √3)


Now, the slope (m2) of eq. (ii) is (2 + √3)


Let θ be the angle between the given two lines.



Putting the values of m1 and m2 in above eq., we get




[(a – b)(a + b) = (a2 – b2)]





tan θ = √3


θ = tan-1(√3)


θ = 60°


Hence, the required angle is 60°


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