the cosine of a sum formula 23 videos

Polygon Angle Sum
Geometry Polygons
How to derive the formula to find the sum of angles in any polygon.
triangle angle sum diagonal polygon 
The Law of Cosines
Geometry Basic Trigonometry
How to define and use the law of cosines.
law of cosines ratios triangles 
Triangle Angle Sum
Geometry Triangles
How to apply the triangle angle sum theorem.
triangle angle sum theorem 180 degrees 
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 
Equiangular Polygon Sums
Geometry Polygons
How to find the measure of one angle in any equiangular or regular polygon.
equiangular regular congruent triangles sum 
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 
Equation of a Circle
Geometry Pythagorean Theorem
How to derive the equation for a circle using the distance formula.
distance formula radius center circle 
Distance Formula
Geometry Pythagorean Theorem
How to derive the equation for the distance between two points using the Pythagorean Theorem.
distance coordinate plane ordered pair segment 
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 
Supplementary and Complementary Angles
Geometry Geometry Building Blocks
How to identify supplementary and complementary angles.
angles sum right angle 
Area of Triangles
Geometry Area
How to derive the area of a triangle formula using the rectangle area formula.
area triangles rectangles altitude 
Area of a Segment
Geometry Area
How to derive the area of a segment formula.
segment sector triangle area radius central angle shaded area 
Inverse Trigonometric Functions
Geometry Basic Trigonometry
How to use inverse trig functions to find angles in right triangles.
trigonometry right triangle inverse sine cosine tangent 
Area of Regular Polygons
Geometry Area
How to derive the formula to calculate the area of a regular polygon.
area apothem side hexagon isosceles triangle perimeter equilateral equiangular 
Area of Circles
Geometry Area
How to derive the formula to calculate the area of a circle.
circle radius circumference area 
Area of a Sector
Geometry Area
How to derive the formula to calculate the area of a sector in a circle.
sector central angle intercepted arc circle radius area 
Surface Area of Cylinders
Geometry Area
How to prove the surface area of a cylinder formula.
circle lateral area circumference 
Area of Kites and Rhombuses
Geometry Area
How to derive the area formula of a kite based on the rectangle formula; how to calculate the area of a rectangle using diagonal lengths.
kite area diagonals consecutive sides vertex angle non vertex angle bisect perpendicular rhombus 
Area of Parallelograms
Geometry Area
How to find the area of any parallelogram using rectangle area formulas.
area of rectangles base times height