the cosine double angle formulas 65 videos

The Law of Cosines
Geometry Basic Trigonometry
How to define and use the law of cosines.
law of cosines ratios triangles 
Angle of Elevation and Depression
Geometry Basic Trigonometry
How to define an angle of elevation or an angle of depression.
trigonometry angle of elevation angle of depression 
Supplementary and Complementary Angles
Geometry Geometry Building Blocks
How to identify supplementary and complementary angles.
angles sum right angle 
Inscribed Angles
Geometry Circles
How to calculate the measure of an inscribed angle.
inscribed angle intercepted arc central angle congruent arcs 
Polygon Angle Sum
Geometry Polygons
How to derive the formula to find the sum of angles in any polygon.
triangle angle sum diagonal polygon 
Remote Interior Angles
Geometry Triangles
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
Geometry Reasoning, Diagonals, Angles and Parallel Lines
How to define corresponding angles and their special properties.
parallel lines angles congruence 
Angle Bisectors
Geometry Geometry 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
Geometry Constructions
How to duplicate an angle using a compass and straightedge.
congruent angles construction compass straightedge 
Trigonometric Ratios: Cosine
Geometry Basic Trigonometry
How to define the cosine ratio and identify the cosine of an angle in a right triangle.
trigonometry ratio right triangle sine SOH CAH TOA 
Solving Formulas
Geometry Area
How to strategize about solving formulas for variables; how to solve the area of a rectangle formula for base and height; how to solve the area of a triangle formula for base and for height.
formulas isolating a variable rectangle area triangle area trapezoid area regular polygon area 
Exterior Angles of a Polygon
Geometry Polygons
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 
Angles in Semicircles and Chords to Tangents
Geometry Circles
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 
Alternate Interior Angles
Geometry Reasoning, Diagonals, Angles and Parallel Lines
How to define alternate interior angles and their special properties.
parallel lines angles congruence interior transversal 
Alternate Exterior Angles
Geometry Reasoning, Diagonals, Angles and Parallel Lines
How to define alternate exterior angles and their special properties.
parallel lines angles congruence exterior transversal 
Triangle Angle Sum
Geometry Triangles
How to apply the triangle angle sum theorem.
triangle angle sum theorem 180 degrees 
Angles: Types and Labeling
Geometry Geometry Building Blocks
How to label an angle and how to differentiate between acute, right, obtuse, and straight angles.
angle acute right obtuse straight vertex side 
Adjacent Angles
Geometry Reasoning, Diagonals, Angles and Parallel Lines
How to define adjacent angles.
vertex side coplanar 
Triangle Side and Angle Inequalities
Geometry Triangles
How to determine the relationship between the side inequalities and angle inequalities in a triangle.
angles smallest to largest sides smallest to largest 
Vertical Angles
Geometry Reasoning, Diagonals, Angles and Parallel Lines
How to define and identify vertical angles.
vertex intersecting lines congruent