Question

Question 3 Find the distance between P(x1,y1) and Q(x2,y2) when:

(i) PQ is parallel to the y-axis,

(ii) PQ is parallel to the x-axis.

Class X1 - Maths -Straight Lines Page 211

Answer 1

(i) PQ is parallel to the Y-axis.
it means the x - co-ordinates of P and Q are same .I.e, x₁ = x₂
so, distance between PQ = √{(x₂ - x₁)² + (y₂ -y₁)²}
= √{0 + (y₂ -y₁)²}
= √(y₂ -y₁)²
= |y₂ -y₁| unit

(ii) PQ is parallel to X - axis .
it means the y - co-ordinate of P and Q are same . i.e y₂ = y₁
so, distance between PQ = √{(x₂ - x₁)² + (y₂ -y₁)²}
= √{(x₂ - x₁)² + 0²}
= √(x₂ - x₁)²
= |x₂ - x₁| unit