Foundation and Higher · parallel lines

Can you name the three angle rules for parallel lines?

“Z angles” won’t get
you the mark…

two parallel lines, one line across —

8 angles

but only two different sizes

three rules tell you which match

rule 1 of 3

Alternate angles

1. Find the Z shape.

2. The angles in its two corners
are equal.

✓ Write: alternate angles
are equal

rule 2 of 3

Corresponding angles

1. Find the F shape.

2. Same position under each arm,
so they are equal.

✓ Write: corresponding angles
are equal

rule 3 of 3

Co-interior angles

1. Find the C shape.

2. Inside the C they are not equal.
They add up to 180°.

✓ Write: co-interior angles
add up to 180°

for the mark, write the name —

Alternate

Z shape · equal

Corresponding

F shape · equal

Co-interior

C shape · add up to 180°

“Z angles” scores nothing —
examiners want the proper name.

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