Sides of a Triangle(Lengths)

1

The addition of the lengths of any two sides of a triangle must be greater than the third.

a b

ca + b >c a+ c> b c + b>a

1

Angles of a Triangle

2

Sum to 180˚

B

A C

m<A + m< B +m< C = 180˚

2

Exterior angle of a Triangle

3

The sum of the two non-adjacent angles of the triangle is equal to the measure of the exterior angle.

B

A C D

m<A + m<B = m<BCD

3

Special Right Triangle(30˚, 60˚, 90˚)

4

Side opposite 30˚= ½ hypotenuseSide opposite 60˚= ½ hypotenuse

60

Hypotenuse Side opp 30

30

Side opp 60

4

3

Special Right Triangle(45˚, 45˚, 90˚)

5

Hypotenuse = leg 45

Hyp Leg

45

Leg

5

2

Similar Triangles~

6

• corresponding angles are congruent• corresponding sides are in proportion.

6

Isosceles Triangle

7

A triangle that contains two congruent sides and angles

7

Isosceles Right Triangle

8

45

Hyp Leg

45

Leg

8

(45˚, 45˚, 90˚)

Median of a triangle

9

A line that is drawn form the vertex of a triangle to the midpoint

of the opposite side

9

Altitude of a Triangle

10

The altitude of a triangle is a line segment extending from any vertex of

a triangle perpendicular to the line containing the opposite side.

10

Altitude