
8 Chapter 1
angle magnets solution
Angle Magnets Solution
Which of these angles matches the mystery angle?
62º 72º 45º 67º
?º
…and this marking
means it’s a
right angle = 90º.
We know that these two angles
come together to make this angle…
18º + ?º = 90º
18º + 72º = 90º
You could have done 90–18 to find the 72º,
or you could just test all the magnets you were
given to find one that fits—making 90º.
Q:
I checked that mystery angle with a protractor and it
wasn’t 72º—so how come you’re saying it is?
A: In geometry, unless you’re specifically told to measure
an angle, assume that the drawing isn’t accurate, but that the
numbers on the sketch are. We calculate missing angles rather
than measure them.
Q:
What about all the other lines on the diagram? Do we
know if they’re straight?
A: The other line segments on the sketch re ...