† Chapter 01, Hanna’s Teaching Notes on Geometry Angles
01 Definition and the method of writing the name of the angle Q•
P
R When two lines, such as PQ and QR, intersect at point Q then the angle is formed at this point or vertex Q and between the two lines is the angle which is usually named ^ ^ by the point of intersection i.e. angle Q or Q or by three letters PQ R such that the middle letter represents point Q, where the lines PQ and QR intersect.
D # $
G
" ! • E
H
If more than two lines intersect at one point then we must name the required angle by three letters or by our own single letter. For example the three lines HD, ED and GD intersect at the point D. ^ ∴ D might be angle α or angle β or angle (α + β) . ^ ∴ α = ED G , ^ β = ED H, ^ Φ = DE G, ^ (α + β) = GD H and ^ θ = DE H
Book 1, Hanna’s Series
1