This geometry video provides a basic introduction into triangles. It explains how to calculate the measure of an interior angle of a triangle as well as the exterior angle. The sum of all three interior angles is 180. The exterior angle is the sum of the two remote interior angles according to the exterior angle theorem. In addition, this video explains how to calculate the length of the midsegment of a triangle. It contains plenty of examples and practice problems. Polygons: https://www.youtube.com/watch?v=E_-3ulbtcLk Quadrilaterals: https://www.youtube.com/watch?v=ogcH3eM5beM Skew Lines: https://www.youtube.com/watch?v=cemF45vNOhg Points, Lines, Planes, & Segments: https://www.youtube.com/watch?v=dDWjhRfBsKM Number of a Diagonals In a Polygon: https://www.youtube.com/watch?v=jZYL2TUrYSw ___________________________________ Ratios and Proportions - Means Extreme: https://www.youtube.com/watch?v=tFCrFa0mDi4 Similar Triangles: https://www.youtube.com/watch?v=YiFwvAFk-xs Similar Triangles - Enlargement Ratios: https://www.youtube.com/watch?v=r7m424e3Kdc Triangle Similarity - SSS, SAS, & AAA: https://www.youtube.com/watch?v=VXlFEilh-cw Triangle Proportionality Theorem: https://www.youtube.com/watch?v=EQpguitDfGU Altitude on Hypotenuse Theorem: https://www.youtube.com/watch?v=RiTp3vyWe0o ___________________________________ Pythagorean Theorem: https://www.youtube.com/watch?v=d8EA5TxGzcY The Distance Formula: https://www.youtube.com/watch?v=YDvUy5VYm9E Distance Between 2 Points - 3D: https://www.youtube.com/watch?v=0c6cP2zLC2c Final Exams and Video Playlists: https://www.video-tutor.net/ Full-Length Videos and Worksheets: https://www.patreon.com/MathScienceTutor/collections