Classifying Triangles by SidesIf all 3 sides arecongruent - Equilateral If no sides are If at least 2 sides are congruent - congruent - isosceles Scalene
Classifying Triangles by Angles All angles < 90°,then ACUTE triangle One angle > 90°, then OBTUSE triangle RIGHT triangle if one angle = 90°
Now you try… Classify each triangle by sides and anglesA. B. C.
Triangle Vocabulary Vertex/Vertices The point(s) at which the sides meet Adjacent Two sides are adjacent if they intersect (touch) A C B
Vocab continued… Interior angle Angle formed on the interior of the triangle Exterior angle Angle formed on the outside of the triangle A exterior angle Interior angle C B
Triangle Sum Theorem The sum of the interior angles of a triangle is 180°
Exterior Angle Theorem The measure of an exterior angle of a triangle is equal to the sum of the two nonadjacent interior angles. Example: m∠1=m∠A+ m∠B B 1 A C
Now you try… Find the measure of each angle (hint: what istheir sum?) 2x + 10 x x+2
Practice BGiven that ∠ A is 40º and∠B is 28º, what is the measure of∠BCD? A C DWhat is the measure of ∠ACB?
Vocabulary for Right Triangles Legs The sides that form the right angle Hypotenuse The side that is opposite the right angle Hypotenuse Legs
Corollary to the Triangle Sum Theorem In a right triangle, the the acute angles are complementary.
Now you try…A. Using the triangle below, what is the length of the hypotenuse?B. What about the lengths of the legs?C. If one of the acute angles has a 13 measure of 35 , give the measure of the other two 12 angles. 5
Vocabulary for IsoscelesTriangles Legs The two sides that are congruent Base The side that isn’t a leg Base Angles The angles formed at each end of the base, which are congruent Vertex Angle The angle formed by the legs
Isosceles triangle Legs Vertex Angle Base Base Angles
Now you try… AA. Given the isosceles triangle, find the measure of side AC.B. Find the measure of the missing angles. 15 75º B C 7
Last bit of practice…Find the two missing interior angle measures. 80 53
Resources All template objects/graphics from Microsoft PowerPoint. All triangles drawn using Microsoft PowerPoint.