Chapter 4
4.1 Apply Properties and 4.7 use Isosceles and Equilateral Triangles
Classify Triangles by Sides p.217
1. Scalene
2. Isosceles
3. Equilateral
Classify Triangles by Angles
1. Acute
2. Right
3. Obtuse
4. Equiangular
Interior and Exterior Angles p.218
Interior Angles: _________, _________, _________
Exterior Angles: _________, _________, _________
THEOREM 4.1
Triangle Sum Theorem
p.218
Example:
THEOREM 4.1
Exterior Angle Theorem
p.219
The sum of the measures of the ________________ angles of a
triangle is ________.
(Draw your own)
The measure of an _____________________ angle of a triangle
is equal to the ___________ of the measures of the two
nonadjacent interior angles.
Example 3:
Corollary to the Triangle
Sum Theorem
p.220
The ___________ angles of a ________________ triangle
are _________________________________.
Example 4:
Section 4.7 p.264
THEOREM 4.7 Base Angles Theorem
If the two sides of a triangle are _____________________,
then the _______________ ________________________
them are _______________________.
Example 1:
THEOREM 4.8
Converse of Base Angles Theorem
If the two angles of a triangle are _____________________,
then the _______________ ________________________
them are _______________________.
**RECALL EQUILATERAL TRIANGLES
HAVE THREE CONGRUENT SIDE**
Corollary to the Base Angle Theorem
If a triangle is _____________________,
then it is ___________________________.
Corollary to the Converse of the
Base Angle Theorem
If a triangle is _____________________,
then it is ___________________________.
Example 2:
Example 3:
NOTES SUMMARY
1. Can you find the measure of the third angle of a triangle if you know the measures of the
other two angles?
2. Can a right triangle be obtuse?
3. Can an obtuse triangle have more than one obtuse angle?
4. Can a right triangle have more than one right angle?
5. Define the vertex angle in an isosceles triangle?
6. Is an equilateral triangle isosceles?