ShmoopTube

00:02

Here’s your shmoop du jour, brought to you by vertical angles.

00:06

You have to figure their calves are starting to get pretty tired.

00:10

How many angles must be equal to the measure of angle 1?

00:13

And here are the potential answers…

00:16

Okay, so believe it or not, the key word in this problem isn’t “angle” or “measure” or even “equal.”

00:22

It’s the word “must.”

00:24

The fact is, based on the information given, there are other angles that could be equal to 1…

00:28

…but we don’t know for sure. And why don’t we know for sure?

00:32

Because we’re never told that the two horizontal-ish lines are actually parallel.

00:36

They certainly look parallel, but we don’t want to go assuming that things are just as they appear.

00:41

That’s what got us in trouble at last year’s Christmas party.

00:45

The only angle we know beyond a shadow of a doubt has the same measure as angle 1 is angle 3…

00:51

…because the two are vertical angles. And by definition, vertical angles must have equal measure.

00:56

So our answer is most decidedly B – uno angle, por favor.

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