Teach GCSE Maths

Lines:parallel and

perpendicular

Teach GCSE Maths

Lines: parallel and Lines: parallel and perpendicularperpendicular

© Christine Crisp

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We use one, two, or sometimes three pairs of arrows to mark parallel lines.

Parallel lines NEVER meet . . . however far we draw

them.

These lines are parallel.

A

B

C

D

We can write AB CD

“AB is parallel to CD”

A

B

CD

Another line may cross the parallel lines.

Transverse

These angles . . .

are called opposite angles.

Can you see why opposite angles are equal?

a a

ANS: Each is 180 b because of the straight lines.

b

When lines cross we get angles.

a a b 180

These angles . . .

are called opposite angles.

Can you see why opposite angles are equal?

ANS: Each is 180 b because of the straight lines.

When lines cross we get angles.

a a b 180

These angles . . .

are called opposite angles.

Can you see why opposite angles are equal?

ANS: Each is 180 b because of the straight lines.

When lines cross we get angles.

The angle between them is 90

These lines are perpendicular.

This line has letters at each end.

The full name for AB is a line segment.

A B

A line segment has a start and an end so it has a certain length.

We often refer to line segments as lines but you need to know what is meant if you do meet the full name.

SUMMARYLine

s

a a

Opposite angles are equal.

Lines at 90 are perpendicular.

A line segment has a start and an end so it has a certain length.

Parallel lines NEVER meet.

transverse

Parallel

Exercise1. Find a line

(a) parallel to AB (b) perpendicular to EF

A

G

B

H

D

J

I

E

C F

K

Answers:

A

G

B

H

J

I

E

C F

K

(a) AB GH

D

Exercise1. Find a line

(a) parallel to AB (b) perpendicular to EF Answers:

A

G

B

H

J

I

E

C F

K

(a) AB GH

D

Exercise1. Find a line

(a) parallel to AB (b) perpendicular to EF Answers:

(b) IJ is perpendicular to EF