Formal proofs present the oh-so-mathematical evidence in two columns: one for the statement they are claiming is true, and the other for the reasoning behind them.

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Rhombi

Centers of a Triangle

Inscribed Angles

Geometric Word Problems

Converting Between Degrees and Radians

Coordinate Geometry

Proving Triangles Congruent

Cosines

Properties of Equality and Congruence

SSS Postulate

Perimeter of Irregular Shapes

Proving Lines are Perpendicular

Transformations

Volumes of Prisms and Cylinders

Cubes: Surface Area and Volume

Surface Area of a Cube

Similar Figures

Lines, Segments and Rays

Tangent Half-Angle Formula

Translations and Functions

The Tangent Function

Perimeter and Circumference

Finding the Distance Between Two Points

SOHCAHTOA

Attributes of Circles

Midsegment Theorem

ACT Math 2.2 Coordinate Geometry

Constructions

Special Right Triangles

Triangles

SAS, ASA, AAS

Verifying Trig Identities

Linear Pairs

Transformaciones

Sines

Collinearity

Surface Area of Cylinders

Area Formulas

Proving Triangles Congruent 2

Volume

Secant Angles

Polygons

Slopes of Parallel and Perpendicular Lines

Equations of Circles

Volumes of Pyramids and Cones

Area of a Sector

Area of an Irregular Shape

Triangle Inequality Theorem

Angles of a Polygon

Vertical Angle Theorem

Law of Cosines

Volumen de un Cubo

Angles

Area

Coordinates and Distance Formula

Law of Sines

Characteristics of Parallelograms

Proving Lines are Parallel

A Midsummer Night's Dream

Perimeter of a Rectangle

Complementary and Supplementary Angles

Exterior and Remote Interior Angles

Parallel Lines and Transversals

Solving Trigonometric Equations

30-60-90 Triangle

Introduction to 3D Geometry