Download Geometry Facts

Geometry Facts
A straight angle (or line) = 180°
A right angle = 90°
A circle = 180°
a
C
A
C
C
A
b
When two lines are parallel, they will never
cross paths, no matter how far they are
extended.
D
When two angle meet to form a right angle,
they are called comlementary. Remember,
complementary angles form a corner. Complementary angles add up to 90°
∠BAC and ∠BAD are complementary.
B
d
When two lines cross, vertical angles or
opposite angles are equal or congruent.
∠a = ∠b and ∠c = ∠d
B
A
c
D
When two angle meet to form a straight angle,
they are called supplementary. Remember,
supplementary angles form a straight line.
Supplementary angles add up to 180°
∠BAC and ∠CAD are supplementary.
1
2
3 4
5 6
7 8
B
D
When two parallel lines are intersected by a
transversal, four angles are created at each
point of the intersection.
The four acute angles are equal.
(∠2, 3, 6, 7)
The four obtuse angles are equal.
(∠1, 4, 5, 8)
Each acute angle is supplementary to each
obtuse angle.