Geometry Help

Looking for some Geometry Help? Our materials here review the basic terms and concepts in geometry and provide further lessons to help you develop your understanding of geometry and its applications to solving problems in real life.

Geometry is about the shape and size of things. It is the study of points, lines, angles, shapes, their relationships, and their properties.

Videos have been included in almost all the following topics to help reinforce your understanding.



Geometry Lessons

Basic Geometry Terms - Points, Lines, Line Segments, Midpoints, Rays, Planes, Space
Pairs of Lines - Intersecting Lines, Parallel Lines, Perpendicular Lines, Skew Lines

Naming an Angle, Angles Around a Point
Measuring Angles Using a Protractor
Drawing Angles Using a Protractor

Types of Angles - Right Angles, Acute Angles, Obtuse Angles, Straight Angles Pairs of Angles
Complementary & Supplementary Angles
Vertical Angles,
Corresponding Angles,
Alternate Interior & Exterior Angles

"Find the angle" problems



Types of Triangles
Right, Acute, Obtuse Triangles
Equilateral, Isosceles, Scalene Triangles

Special Right Triangles
3-4-5 Triangles,
45°-45°-90° Triangles,
30°-60°-90° Triangles

Pythagorean Theorem
Pythagorean Triples
Pythagorean Theorem Word Problems
Converse of the Pythagorean Theorem

Congruent Triangles
SSS rule, SAS rule, ASA rule, AAS rule
Hypotenuse Leg (HL)

Similar Triangles - AA rule, RAR rule

Triangle Inequality - Triangle Inequality Theorem, Angle-Side Relationship

Triangle Sum Theorem
Exterior Angle Theorem
Interior Angles of a Triangle
Exterior Angles of a Triangle
Angles of a Triangle



Quadrilaterals - Parallelograms, Squares, Rhombus, Rectangles, Trapezoids
Types of Polygons

Angles in Polygons
- Sum of Angles in a Triangle, Dividing Polygons into Triangles, Formula for Sum of Interior and Exterior Angles
Areas of Polygons
Areas of Squares and Rectangles
Areas of Parallelograms
Areas of Triangles
Area of Rhombus
Area of Trapezoids
Area of Shaded Region

Perimeters of Polygons - Squares, Rectangles, Parallelograms, Triangle, Rhombus, Trapezoids



Diameter, Radius, Arc and Tangent of a Circle
Circumference of circle
Area of circle

Length of Arc in a circle
Area of Sector

Tangent to a Circle
Angles involving Tangents & Circles

Degrees and Radians
Arc Length of Circle in Radians

Circle Theorems
Chords of a Circle

The Arrow Theorem
The Bow Theorem
"90 Degrees in Semicircle" Theorem
Alternate Segment Theorem
Quadrilaterals in a Circle
Angles in a Circle

Angles and Intercepted Arcs

Solid Geometry
Volume of Solids
Volume of Cubes
Volume of Rectangular Prisms
Volume of Prisms
Volume of Cylinders
Volume of Spheres
Volume of Cones,
Volume of Pyramids

Surface Area of a Cube
Surface Area of a Prism
Surface Area of a Cylinder
Surface Area of a Cone
Surface Area of a Sphere
Surface Area of a Pyramid
Surface Area of Solids

Geometry Nets

Formulas Explained: Area of Cone, Volume of Cone, Volume of Sphere

Geometrical Formulas
Summary of shapes and formulas

Area Formula: rectangle, parallelogram. rhombus, triangle, regular polygon, trapezium, and circle

Surface Area Formula: sphere, closed cylinder, hollow cylinder, cone and pyramid

Volume Formula: solid cylinder, hollow cylinder, prism, cone, pyramid, and sphere

Coordinate Geometry and Graphs
Coordinate Geometry
Coordinate Plane

Slope of a Line - y-intercept, Negative Slope
Equation of a Line
Graphing Linear Equations
Slope and Intercept of a Linear Equation

Equation of a Line Parallel to the X-axis or Y-axis
Equation of a Line Given its Slope and a Point on the Line
Equation of a Line Given Two Points on the Line

Slopes of Parallel Lines, Slopes of Perpendicular Lines

Midpoint Formula
Distance Formula

Graphing Inequalities
Linear Programming

Graphing Quadratic Functions
Graphical Solutions of Quadratic Functions

Graphing Cubic Functions
Graphing Exponential Functions
Graphing Reciprocal Functions

Sketching the Graphs of some Functions

Geometric Construction
Geometric Construction

Construct and Copy Lines
Construct a Perpendicular Bisector
Construct a Perpendicular Line through a Point
Construct Parallel Lines

Construct a 60° Angle by Constructing An Equilateral Triangle
Construct an Angle Bisector
Construct a 30 Degree Angle
Construct a 45 Degree Angle

Construct A Triangle Given The Length Of Its Three Sides (SSS)
Construct A Triangle Given One Side And Two Angles

Construct A Triangle Given Two Sides And An Angle

Construct a Parallelogram and a Square

Contruct Various Angles & Shapes : 30°, 45 °, 90°, 120°; hexagon, triangle

Locus of a Moving Point

Geometry Transformation
Geometry / Math Tranformations

involves “sliding” the object from one position to another.

involves “flipping” the object over a line called the line of reflection.

involves “turning” the object about a point called the center of rotation.

Dilation involves a resizing of the object. It could result in an increase in size (enlargement) or a decrease in size (reduction).

Geometry Proofs (Videos)
Triangle Medians and Centroids (2D Proof)
Area Circumradius Formula Proof
Proof that the diagonals of a rhombus are perpendicular bisectors of each other

Geometry Practice Questions

Free SAT Practice Questions (with Hints & Solutions) -
Geometry: Questions 1-5, Questions 6-10

Geometry Word Problems



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