Distance formula — Grade 8 Math, what it means and where it is taught
d = √(x2 - x1)2 + (y2 - y1)2.
Taught in Grade 8 Math.
Where it is taught
Practise this idea
5 questions in the course bank use Distance formula, in Equations of Circles, Coordinate Geometry Proofs.
Problem 1
A circle has centre (2, -3) and passes through (6, 0). Write its equation.
Worked answer
(x-2)^2 + (y+3)^2 = 25
r = √16 + 9 = 5
(x-2)2 + (y+3)2 = 25
Problem 2
In (x-h)2 + (y-k)2 = r2, the number on the right is
- r2
- r
- 2r
- the diameter
Worked answer
r2
It stores r2.
A right side of 25 means radius 5.
Problem 3
Find the length of the segment from (0,0) to (6,8).
Worked answer
10
√36+64 = √100
= 10
Problem 4
You want to prove two sides are congruent. Which formula do you use?
Worked answer
distance
Congruent means equal length.
Use the distance formula.
Problem 5
A(0,0), B(4,0), C(4,3), D(0,3). Find the length of a diagonal.
Worked answer
5
(0,0) to (4,3): √16+9 = 5