Angles

Acute angle (def)- angle measure less than 90°

Right angle (def)- angle measure= 90°

Obtuse angle (def)- angle measure greater than 90°

Straight angle (def)- angle = 180° Interior of angle

Exterior of angle

To Name an Angle- A. Use 3 letters (vertex in the middle)B. Number it. C. IF there is ONLY ONE angle with that vertex, you may use a single letter (the vertex).

A D

is NOT appropriate for this sketch b/cvertex 1 there are 3 angles with the vertex B. 2 C

Congruent angles- angles that have = measures.

- measure of an angle

ABD 1

m ABC

B

Adjacent Angles (def)-2 coplanar angles that share a common ray. They must have a common vertex.

• Complementary <‘s are 2 angles whose measures have a sum of 90.

m<1 + m<2 = 90• Supplementary <‘s are 2 angles whose

measures have a sum of 180. m<1 + m<2 = 180

°

or

50° 40°

COMPLEMENTARY ANGLES may or may not be adjacent.

COMPLEMENTARY ANGLES may or may not be

SUPPLEMENTARY ANGLES may or may not be adjacent.

SUPPLEMENTARY ANGLES may or may not be

or

145° 35°

Linear Pair (def)-adjacent angles whose non-common sides form a line. (describes)

• Linear Pairs are Supplementary. If <1 and <2 form a linear pair, then they are supplementary.

m<1 + m<2 = 180

Angle Bisector(def)- is a ray that divides the angle into 2 congruent angles.

A

D

B C

ABD DBC

Angle Addition Postulate- sum of the parts = whole

The angles must be adjacent.

m ABD m DBC m ABC

A D

B C

Vertical Angles(def)- 2 nonadjacent angles formed by intersecting lines (describes)

1

4 2 3

If 2 angles are vertical, then they are congruent. (value)