Question

If slope of one line is 1/4 and other is 5/3 then find the angle between two lines.

(a) 30°

(b) 45°

(c) 90°

(d) 180°

The question was asked in unit test.

My question is based upon Various Forms of the Equation of a Line in section Straight Lines of Mathematics – Class 11

Answer 1

Right answer is (b) 45°

For explanation: If angle between two lines with slopes m1 and m2 is α then tan α = |(m1-m2)/(1+m1*m2)|

tan α = \(|\frac{5/3-1/4}{1+5/3*1/4}| = |\frac{20-3}{12+5}|\) = 17/17 =1 => α = 45°