this one…

this one, t

oo!

Vertical angles are always equal

When two straight lines cross they always create two pairs of

equal opposite angles, called vertical angles.

Each angle has to form a supplementary pair with either of

the angles on the other side of it, so they must be equal.

finding missing angles

Save yourself a ton of

math by spotting equal

pairs of vertical angles.

These two

are equal.

These two are

also equal.

So if y

ou know

…y

ou a

lready know

Two straight

lines cross

Add

ei

ther t

o

the

or

igina

l

angle and y

ou get 180º.

Pick one

angle

The supplements

must be equal

Find its

supplements

&

&

T

his is one

supplement…

…and

here’s the

other one.

Patterns in geometry aren’t just coincidence

These relationships are how geometry works…and to see a

really freaky one, try this:

Do this!

you are here 4 19

On some scrap paper, draw a triangle using a ruler.

Cut the triangle out.

Tear the corners off.

And then put the three corner pieces together with

the points in the middle.

Weird, huh?

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