the cosine double angle formula 187 videos

The Distance Formula in Polar Coordinates
Precalculus Polar Coordinates and Complex Numbers
How to derive the distance formula for polar coordinates.
polar coordinates the law of cosines triangles 
Midpoint Formula
Algebra 2 Graphs of Linear Equations
How to find the midpoint of two points.
midpoint formula 
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 
Radian Measure of Angles
Trigonometry Trigonometric Functions
How to measure angles using degrees or radians.
angle degree measure acute angle right angle obtuse angle radian measure 
Radian Measure of Angles
Precalculus Trigonometric Functions
How to measure angles using degrees or radians.
angle degree measure acute angle right angle obtuse angle radian measure 
The Inverse Cosine Function
Precalculus Advanced Trigonometry
How to restrict the domain of cosine so it will have an inverse function.
inverse functions one to one inverse cosine arccosine 
The Inverse Cosine Function
Trigonometry Advanced Trigonometry
How to restrict the domain of cosine so it will have an inverse function.
inverse functions one to one inverse cosine arccosine 
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 
Find an Equation for the Sine or Cosine Wave
Trigonometry Trigonometric Functions
How to identify the graph of a stretched cosine curve.
sine cosine period amplitude intercepts turning points 
Find an Equation for the Sine or Cosine Wave
Precalculus Trigonometric Functions
How to identify the graph of a stretched cosine curve.
sine cosine period amplitude intercepts turning points 
Angle Inclination of a Line
Precalculus Advanced Trigonometry
How to find the angle of inclination of a line.
angle inclination horizontal lines tangent slope 
Angle Inclination of a Line
Trigonometry Advanced Trigonometry
How to find the angle of inclination of a line.
angle inclination horizontal lines tangent slope 
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 
The Angle Between Vectors
Precalculus Vectors and Parametric Equations
How to compute the angle between two vectors.
dot product angle between vectors position vectors 
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 
The Midpoint and Distance Formulas in 3D
Precalculus Vectors and Parametric Equations
How to derive the formula for the midpoint of a segment in three dimensions.
position vectors the vector from point a to point b the midpoint formula vector addition scalar multiplication 
Adjacent Angles
Geometry Reasoning, Diagonals, Angles and Parallel Lines
How to define adjacent angles.
vertex side coplanar