SIDES
Scalene – all sides have a
Isosceles – at least two of
Equilateral – all three sides
different length (measure)
the sides have the same
measure
have the same measure
11
7
7
5
5
8
3
4
ANGLES
Equiangular – all
three angles are equal
5
Right – one angle is Obtuse – one angle
Acute – all three
a right angle and the
other two are acute
angles are acute
is obtuse and the
other two are acute
30°
60°
51°
46°
104°
39°
Parts of the Triangle:
38°
72°
- _____ ABC
- Points A, B, and C are _______________________
- side BC is the side _________________________
Parts of the Isosceles Triangle:
Parts of the Right Triangle:
-
- sides that form the right angle are
___________________________
two congruent sides are called
the legs
- 3rd side is the _________________se - side opposite the right angle is the
___________________________
use
Theorem 4.1: TRIANGLE SUM THEOREM
The sum of the measures of the interior angles
of a triangle is _________
Theorem 4.2: EXTERIOR ANGLE THEOREM
The measure of an exterior angle of a triangle is
equal to the sum of the measures of the two
__________________________ angles.
Practice: Find the measure of the numbered angles.
1.
2.
1
2
3
50
58
3. Solve for x:
(2x+3)o
(4x+8)o
51o
2
6
125
3
4
20
7
1
22
4
5
8
9
65
85
4. The front face of the wheelchair ramp
forms a right triangle. The measure of one
acute angle is eight times the measure of the
other. Find the measure of each acute angle.
5. Solve for x: Find the angle measures and classify the triangle by its angles.
m  A = (3x – 17)
m  B = ( x + 40)
m  C = ( 2x – 5)
6. Find the values of x and y. Pay attention to the markings!
6. Classify RST by its sides. Then determine if the triangle is a right triangle. **Hint:
Use distance to classify by sides, and slopes to determine if it is a right triangle – what
is true about the lines if it is a right triangle?
R
S
T