Complementary Angles
Two Angles are Complementary if they add up to 90 degrees (a Right Angle).
|
These two angles (40° and 50°) are Complementary Angles, because they add up to 90°.
Notice that together they make a right angle.
|
 |
| |
|
|
But the angles don't have to be together.
These two are complementary because 27° + 63° = 90°
|
 |
| |
 |
If the two angles add to 90°, we say they "Complement" each other.
Complementary comes from Latin completum meaning "completed" ... because the right angle is thought of as being a complete (full) angle. |
| |
|
|
| |
 |
Spelling: be careful, it is not "Complimentary Angle" (with an "i") ... that would be an angle you get for free! |
Right Angled Triangle
In a right angled triangle, the two acute angles are complementary, because there are 180° in a triangle and 90° have been accounted for by the right angle.
|
 |
Note: A related idea is Supplementary Angles - those add up to 180°
|
HOME
