Ray — Geometry, what it means and where it is taught
One endpoint and everything beyond it in one direction. Written AB.
Taught in Geometry.
Where it is taught
What uses it later
This idea is needed for:
- Polar axis — The ray pointing along positive x, from which θ is measured.
Practise this idea
4 questions in the course bank use Ray, in Definitions, Postulates & Reasoning, Similarity & Proportionality, Polar Coordinates.
Problem 1
Does AB stop at B? Answer yes or no.
Worked answer
no
A ray starts at A and continues past B forever.
So it does not stop.
Problem 2
Three rays from O make angles m∠ AOB = (x)°, m∠ BOC = (2x)°, and m∠ AOC = 72°. Find m∠ BOC.
Worked answer
48
x + 2x = 72
x = 24
m∠ BOC = 48°
Problem 3
A 5 ft person casts a 4 ft shadow. A tree casts a 32 ft shadow. Find the tree height.
Worked answer
40
54 = h32
h = 40 ft
Problem 4
What is the graph of θ = 45°?
- A line through the origin
- A circle
- A ray of length 45
- A parabola
Worked answer
A line through the origin
Every distance in that one direction, including negative r backwards