1. Report by Jennifer Johnson
Triangles
Report by
Jennifer Johnson

2. What is a Triangle?
A polygon
Three sides
Three angles

3. Types of Triangles By Sides By Angles Scalene Isosceles Equilateral
Acute
Obtuse
Right

4. A triangle with no sides congruent.
Scalene
A triangle with no sides congruent.

5. A triangle with at least 2 congruent sides
Isosceles
A triangle with at least 2 congruent sides

6. A triangle with all sides congruent
Equilateral
A triangle with all sides congruent

7. A triangle with all acute angles

8. A triangle with one obtuse angle

9. A triangle with one right angle

10. Special Theorems
The sum of the angles of a triangle equals 180 degrees.
If a triangle is an isosceles triangle, then the angles opposites the congruent sides are congruent.
If a triangle is an obtuse triangle, then the side opposite the obtuse angle is the longest side of the triangle.

11. More Theorems
If a triangle is an equilateral triangle, the all angles of the triangle are congruent and equal 60 degrees.
The two acute angles of a right triangle are complementary.

12. Prove: The two acute angles of a right triangle are complementaryB
Given: ABC, <A is a right angle C A
Statements
Reasons
1. ABC is a triangle, <A is a right angle.
2. If <A is a right angle, then it’s measure = 90 
3. m<A + m<B + m<C = 180 .
4. 90+ m<B + m<C = 180 
5. m<B +m<C = 90 
6. <B and <C are complementary
1. Given
2. All right angles equal 90 
3. The sum of the angles of a triangle equal 180 
4. Substitution from step 2 into step 3
5. Subtraction property
6. If the sum of the measures of two angles equals 90  , then the angles are complementary.