8-4 Triangles Objective: Students find unknown angles and line segment lengths in triangles.
Vocabulary Acute triangle- has 3 acute angles Right triangle- has 1 right angle Obtuse triangle- has 1 obtuse angle Equilateral triangle- has 3 congruent sides and 3 congruent angles
Vocabular y Isosceles triangle- has at least 2 congruent sides and 2 congruent angles Scalene triangle- has no congruent sides and no congruent angles Midpoint- of a segment is the point that divides the segment into 2 congruent segments Altitude- of a triangle is a perpendicular segment from a vertex of the triangle to the line containing the opposite side
Triangle Sum Theorem WordsNumbersAlgebra The interior angle measures of a triangle add to 180º 43º79º 58º = 180 rºrº sºsºtº r + s + t = 180
Example 1 Find Angles in Acute, Right, or Obtuse Triangles. Find x in the acute triangle 42º 63º xºxº Find x in the right triangle 37º xºxº
Example 2 Find the angle measure in the equilateral triangle Finding Angles in Equilateral, Isosceles, or Scalene Triangles. mºmºmºmº mºmº 4pº Find the angle measure in the scalene triangle 3pº2pº
Example 3 Finding the Length of a Line Segment In the figure, M is the midpoint of PQ and RM is an altitude of △ PQR. Find the length of RM. R PQ 24 m M 20 m
Problem #1 Find q in the acute triangle.