1.5 triangles.notebook
September 18, 2012
Things you may assume
• You may assume that lines are straight
• You may assume that 2 lines intersect at a point
• You may assume that all points on a line are
collinear and that all points shown in a diagram are
coplanar unless planes are drawn to show them
noncoplanar
1.5 Triangles
Sep 16­7:53 AM
Things you may not assume
• That just because 2 lines look parallel that they are
parallel-they must be marked parallel
• That just because 2 lines look perpendicular that they
are perpendicular-they must be marked
• Pairs of angles, segments, or polygons are congruent
just because they look that way-they must be marked
Sep 16­7:53 AM
Ex.
• Which pairs of lines are ⊥?
• Which pairs of lines are ||?
Sep 16­7:53 AM
Sep 16­7:53 AM
Define
Ex.
• What does it mean if 2 polygons are congruent?
• Which triangles below are ≅?
Sep 16­7:53 AM
• Right Triangle
Sep 16­7:53 AM
1
1.5 triangles.notebook
Define
September 18, 2012
Define
• Acute Triangle
• Obtuse Triangle
Sep 16­7:53 AM
Define
Sep 16­7:53 AM
Define
• Scalene Triangle
Sep 16­7:53 AM
Define
• Equilateral Triangle
Sep 16­7:53 AM
Parts of an Isosceles Triangle
• Isosceles Triangle
Sep 16­7:53 AM
Sep 16­7:53 AM
2
1.5 triangles.notebook
September 18, 2012
Sep 18­9:18 AM
3