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Supplementary Angles
What Are Supplementary Angles?
When two angles add up to 180 degrees they are called
Supplementary Angles
. For an example, closely look at the diagram below. We have a straight line which is a 180° angle. This 180° angle is cut in two by ray
EF
. So now the 180° is divided in to two smaller angles that add up to 180°. Now let us express this definition in geometric math terms. Supplementary angles in geometry have the following characteristics.
First let's start with a
Straight Angle
:
∠DEC
. We already know that
Straight Angle
are 180°.
Now let us draw a Ray
EF
. The angle at
∠FEC
is 33°.
If we look at the diagram below, the two adjacent angles are
∠DEF
and
d∠FEC
. The sum of these two angles are 180° because they form a
Straight Angle
.
We know 180° minus
∠FEC
equals
∠DEF
.
∠FEC
equals 33°. So 180° minus 33° equals 147°. So the angle at
∠DEF
equals 147°.
See More About Angles