300 likes | 515 Views
4.1 Triangles & Angles. A Triangle. Is a figure formed by three segments Joining three noncollinear points ….it has Sides ….. And Angles. Triangles can be classified by sides. Scalene (no sides equal) Isosceles (as least 2 sides equal) Equilateral (3 congruent sides).
E N D
A Triangle • Is a figure formed by three segments • Joining three noncollinear points….it has • Sides….. • And Angles.
Triangles can be classified by sides.. • Scalene (no sides equal) • Isosceles (as least 2 sides equal) • Equilateral (3 congruent sides)
A Triangle can be classified by ANGLES… • Acute (3 acute angles) • Right (1 right angle) • Obtuse (1 obtuse angle) • Equiangular (3 congruent angles)
Triangle Vocabulary • Vertex A • Vertex B • Vertex C
Triangle Vocabulary • Side opposite angle A • Side oppositeangle B • Side opposite angle C
Right Triangles • Hypotenuse • Leg • Leg
Isosceles Triangle • Base • Leg • Leg
When the sides of a triangle are extended….the triangle has • Interior Angles • Exterior Angles
Complete each sentence with the word always, sometimes or never.
Theorem 4.1-Triangle Sum Theorem • The sum of the interior angles of a triangle is 180 degrees.
Theorem 4.2-Exterior Angle Theorem • The measure of an exterior angle of a triangle is equal to the sum of the two nonadjacent interior angles.
A corollary to a theorem • Is a statement that can be proved easily using a theorem • Think of it as a mini-theorem.
Corollary to the triangle sum theorem • The acute angles of a right triangle are complementary.