# triangle angle sum   82 videos

• #### Triangle Angle Sum

##### GeometryTriangles

How to apply the triangle angle sum theorem.

triangle angle sum theorem 180 degrees
• #### Polygon Angle Sum

##### GeometryPolygons

How to derive the formula to find the sum of angles in any polygon.

triangle angle sum diagonal polygon
• #### Supplementary and Complementary Angles

##### GeometryGeometry Building Blocks

How to identify supplementary and complementary angles.

angles sum right angle
• #### Triangle Side and Angle Inequalities

##### GeometryTriangles

How to determine the relationship between the side inequalities and angle inequalities in a triangle.

angles smallest to largest sides smallest to largest
• #### Exterior Angles of a Polygon

##### GeometryPolygons

How to find the sum of the exterior angles in a polygon and find the measure of one exterior angle in an equiangular polygon.

exterior angle sum of angles equiangular polygon
• #### Equiangular Polygon Sums

##### GeometryPolygons

How to find the measure of one angle in any equiangular or regular polygon.

equiangular regular congruent triangles sum
• #### Special Isosceles Triangle Properties

##### GeometryTriangles

How to identify a segment from the vertex angle in an isosceles triangle to the opposite side.

isosceles triangle angle bisector altitude median
• #### Corresponding Parts of Similar Triangles

##### GeometrySimilarity

How to relate corresponding altitudes, medians and angle bisectors in similar triangles.

similar triangles altitude median angle bisector proportional
• #### Similar Triangles in Circles and Right Triangles

##### GeometrySimilarity

How to determine if two triangles in a circle are similar and how to prove that three similar triangles exist in a right triangle with an altitude.

similar inscribed angles intercepted arc right angle circle
• #### Types of Triangles

##### GeometryGeometry Building Blocks

How to classify a triangle based on its side lengths and angle measures.

equiangular equilateral isosceles right acute obtuse triangles
• #### Angle of Elevation and Depression

##### GeometryBasic Trigonometry

How to define an angle of elevation or an angle of depression.

trigonometry angle of elevation angle of depression
• #### Isosceles Triangles

##### GeometryTriangles

How to define isosceles triangles, their components and how to determine their properties.

vertex angle leg base base angle converse remote interior angles
• #### Using Sine to Calculate the Area of a Triangle

##### GeometryBasic Trigonometry

How to calculate the area of any triangle using two sides and an included angle.

area of a triangle sine
• #### Area of Triangles

##### GeometryArea

How to derive the area of a triangle formula using the rectangle area formula.

area triangles rectangles altitude
• #### Inscribed Angles

##### GeometryCircles

How to calculate the measure of an inscribed angle.

inscribed angle intercepted arc central angle congruent arcs
• #### Remote Interior Angles

##### GeometryTriangles

How to define exterior angles and their remote interior angles and how to prove their properties.

exterior angle remote interior angle non adjacent angle
• #### Corresponding Angles

##### GeometryReasoning, Diagonals, Angles and Parallel Lines

How to define corresponding angles and their special properties.

parallel lines angles congruence
• #### Angle Bisectors

##### GeometryGeometry Building Blocks

How to label an angle bisector; how to use an angle bisector to find a missing variable.

congruent angles ray
• #### Duplicating an Angle

##### GeometryConstructions

How to duplicate an angle using a compass and straightedge.

congruent angles construction compass straightedge
• #### Angles in Semicircles and Chords to Tangents

##### GeometryCircles

How to prove that an angle inscribed in a semicircle is a right angle; how to solve for arcs and angles formed by a chord drawn to a point of tangency.

inscribed angle semicircle tangent chord intercepted arc