### Triangles - Part I

Lesson by Mike McGarry
Magoosh Expert

Summary
The essence of the content revolves around the fundamental properties and rules governing the geometry of triangles, which are crucial for understanding more complex shapes and for success on the ACT exam.
• Every triangle has exactly three sides and three vertices, with the sum of its internal angles always equating to 180 degrees.
• Triangles cannot have more than one right or obtuse angle, ensuring at least two angles are always acute.
• The largest angle in a triangle is always opposite the longest side, and the smallest angle is opposite the shortest side.
• The Triangle Inequality Theorem states that the sum of any two sides of a triangle must be greater than the third side.
• For any two sides of a triangle, the length of the third side must be greater than the difference and less than the sum of these two sides.
Chapters
00:00
Introduction to Triangles
01:05
Angle Sum Property
05:32
Triangle Inequality Theorem
09:13
Determining the Third Side