Geometric Rules Quick Reference - MathBitsNotebook (Jr) (2024)

Geometric Rules Quick Reference - MathBitsNotebook (Jr) (1)

Geometric Rules Quick Reference
[Junior Level]
MathBitsNotebook.com

Topical Outline | JrMath Outline | MathBits' Teacher Resources
Terms of Use Contact Person: Donna Roberts
Geometric Rules Quick Reference - MathBitsNotebook (Jr) (2)

This is a partial listing of the more popular rules (theorems, postulates, and properties) that you will be using in your study of Geometry.

First a few words that refer to types of geometric "rules":

• A

theorem is a statement (rule) that has been proven true using facts, operations and other rules that are known to be true. These are usually the "big" rules of geometry. A short theorem referring to a "lesser" rule is called a lemma.

• A corollary is a follow-up to an existing proven theorem. Corollaries are off-shoots of a theorem that require little or no further proof.

• A postulate (or axiom) is a statement (rule) that is taken to be true without proof. Euclid derived many of the rules for geometry starting with a series of definitions and only five postulates.

• A property is a quality or characteristic belonging to something.
For example, the real numbers have the associative, commutative and distributive properties.

Your textbook (and your teacher) may want you to remember these "rules" with slightly different wording.
Be sure to follow the directions from your teacher.

Geometric Rules Quick Reference - MathBitsNotebook (Jr) (3) Angles:

Adjacent Angles

Two angles that share a common vertex, a common side, and no common interior points (don't overlap).
m∠ABD and m∠DBC are adjacent. m∠ABC and m∠DBC are not adjacent
Geometric Rules Quick Reference - MathBitsNotebook (Jr) (4)

Linear Pair

Two adjacent angles whose non-common sides for a straight line.

Straight Angles

All straight angles are congruent (equal in measure).
(They all have a measure of 180º.)

Vertical Angles

Vertical angles are congruent (equal in measure).
m∠1 = m∠2
m∠3 = m∠4

Geometric Rules Quick Reference - MathBitsNotebook (Jr) (5)

Triangle Interior Sum

The sum of the measures of the interior angles of a triangle is 180º.

Exterior Angle

The measure of an exterior angle of a triangle is equal to the sum of the measures of the two non-adjacent interior angles.

Angles forming a straight line

Geometric Rules Quick Reference - MathBitsNotebook (Jr) (6)

Angles around a point

Geometric Rules Quick Reference - MathBitsNotebook (Jr) (7)

Complementary Angles

Two angles the sum of whose measures is 90º.

Supplementary Angles

Two angles the sum of whose measures is 180º.

Geometric Rules Quick Reference - MathBitsNotebook (Jr) (8) Triangles:

Pythagorean Theorem

c2 = a2 + b2
In a right triangle, the square of the hypotenuse equals the sum of the square of the lengths of the legs.

Sum of Two Sides

The sum of the lengths of any two sides of a triangle must be greater than the third side.

Longest Side

In a triangle, the longest sideis across from the largest angle.

Largest Angle

In a triangle, the largest angle is across from the longest side

Congruent Triangles

Triangles that are congruent if there corresponding angles are congruent and their corresponding sides are congruent.

Short-cuts to verify congruent triangles

SSS, ASA, AAS, SAS, HL(in right triangles)

Angle-Angle (AA) Similarity

If two angles of one triangle are congruent to two angles of another triangle, the triangles are similar.

Sides of Similar Δs

Corresponding sides of similar triangles are in proportion.

Geometric Rules Quick Reference - MathBitsNotebook (Jr) (9) Parallels:

Corresponding Angles

If two parallel lines are cut by a transversal, then the pairs of corresponding angles are congruent.

Alternate Interior Angles

If two parallel lines are cut by a transversal, then the alternate interior angles are congruent.

Alternate Exterior Angles

If two parallel lines are cut by a transversal, then the alternate exterior angles are congruent.

Interiors on Same Side

If two parallel lines are cut by a transversal, the interior angles on the same side of the transversal are supplementary.

Geometric Rules Quick Reference - MathBitsNotebook (Jr) (10) Quadrilaterals:

Quadrilateral

• is a four sided polygon
• a figure with exactly four sides

Parallelograms

is a quadrilateral w/ both pairs of opposite sides parallel
opposite sides are equal in length

Rectangle

• is a parallelogram with 4 right angles
• two pairs of parallel sides
• opposite sides of equal length

Rhombus

• is a parallelogram with all 4 sides of equal length
• two pairs of parallel sides

Square

• is a parallelogram with 4 sides of equal length and 4 right angles
• two pairs of parallel sides

Trapezoid

• quadrilateral with at least one pair of parallel sides

Isosceles Trapezoid

• is a trapezoid with congruent base angles
• at least one pair of parallel sides
• legs congruent

Kite

• is a quadrilateral with two sets of adjacent sides equal
• not a trapezoid and not a parallelogram

Geometric Rules Quick Reference - MathBitsNotebook (Jr) (11)

Geometric Rules Quick Reference - MathBitsNotebook (Jr) (12) Area (A), Volume (V), Surface Area (SA):

Rectangle

Arectangle = l × w = b • h

l= length; w = width; b = base; h = height

Parallelogram

Aparallelogram = b • h

Triangle

AΔ = ½ • b• h

Trapezoid

Atrapezoid = ½ h (b1 + b2) or decompose

Regular Polygon

Aregular polygon = ½ • a • p

a = apothem; p = perimeter

Circle (circumference)

C = 2πr = πd
r =
radius; d = diameter

Circle (area)

Acircle = πr2

Rectangular Solid
(also called right rectangular prism)

Geometric Rules Quick Reference - MathBitsNotebook (Jr) (13)
SA formula assumes a "closed box" with all 6 sides.

Cube
[special case of rectangular solid with all edges equal)

Geometric Rules Quick Reference - MathBitsNotebook (Jr) (14)
SA formula assumes a "closed box" with all 6 sides. s = side

Cylinder

Geometric Rules Quick Reference - MathBitsNotebook (Jr) (15)
SA formula assumes a "closed container" with a top and a bottom.

Cone

Geometric Rules Quick Reference - MathBitsNotebook (Jr) (16)
SA formula assumes a "closed container", with a bottom. s = slant height

Sphere

Geometric Rules Quick Reference - MathBitsNotebook (Jr) (17)

Right Prism
(rectangular or triangular)

Vright prism = B • h; SA = 2B + p • h
B = area of the base; h = height; p = perimeter of base

Pyramid
[assuming all of the faces (not the base) are the same]

Geometric Rules Quick Reference - MathBitsNotebook (Jr) (18)
B
= area of the base; h = height; p = perimeter of base; s = slant height

Geometric Rules Quick Reference - MathBitsNotebook (Jr) (19)

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Topical Outline | JrMath Outline | MathBitsNotebook.com | MathBits' Teacher Resources Terms of Use Contact Person: Donna Roberts


Geometric Rules Quick Reference - MathBitsNotebook (Jr) (2024)

FAQs

Geometric Rules Quick Reference - MathBitsNotebook (Jr)? ›

What are the basic rules of geometry? Geometry studies shapes that are all closed by arcs or line segments. Two-dimensional figures, such as squares and rectangles, have only two dimensions, length and width. Three dimensional figures are also closed, and are defined by length, width, and height.

What are the basic geometric rules? ›

What are the basic rules of geometry? Geometry studies shapes that are all closed by arcs or line segments. Two-dimensional figures, such as squares and rectangles, have only two dimensions, length and width. Three dimensional figures are also closed, and are defined by length, width, and height.

What are the 12 theorems of geometry? ›

The geometry theorems are: Isosceles Triangle Theorem, Angle Sum Triangle Theorem, Equilateral Triangle Theorem, Opposite Angle Theorem, Supplementary Angle Theorem, Complementary Angle Theorem, 3 Parallel Line Theorems, Exterior Angle Theorem, Exterior Angles of a Polygon and Interior Angles of a Polygon.

What are the rules of triangle theorems? ›

Theorem 1: The total of the three interior angles in any triangle is 180 degrees. Theorem 2: When a triangle side is constructed, the exterior angle formed is equal to the sum of the interior opposite angles. Theorem 3: The base angles of an isosceles triangle are equivalent.

What are geometry rules called? ›

The rules of Euclidean geometry are called postulates. The five postulates made by Euclid are: Postulate 1: A straight line may be drawn from any one point to any other point. Postulate 2: A terminated line can be produced indefinitely. Postulate 3: A circle can be drawn with any centre and any radius.

What is the formula for the geometric rule? ›

What is the rule for the geometric sequence? Each term of a geometric sequence is formed by multiplying the previous term by a constant number r, starting from the first term a1. Therefore, the rule for the terms of a geometric sequence is an=a1(r)^(n-1).

What is the hardest theorem in math? ›

In number theory, Fermat's Last Theorem (sometimes called Fermat's conjecture, especially in older texts) states that no three positive integers a, b, and c satisfy the equation an + bn = cn for any integer value of n greater than 2.

How to proof geometry theorems? ›

The Structure of a Proof
  1. Draw the figure that illustrates what is to be proved. ...
  2. List the given statements, and then list the conclusion to be proved. ...
  3. Mark the figure according to what you can deduce about it from the information given. ...
  4. Write the steps down carefully, without skipping even the simplest one.

What is the most famous theorem? ›

The Hundred Greatest Theorems
1The Irrationality of the Square Root of 2500 B.C.
2Fundamental Theorem of Algebra1799
3The Denumerability of the Rational Numbers1867
4Pythagorean Theorem500 B.C.
5Prime Number Theorem1896
95 more rows

What is the general rule of a triangle? ›

Triangle Properties

The sum of all the angles of a triangle (of all types) is equal to 180°. The sum of the length of the two sides of a triangle is greater than the length of the third side. In the same way, the difference between the two sides of a triangle is less than the length of the third side.

What is Soh Cah Toa? ›

SOHCAHTOA is a mnemonic device helpful for remembering what ratio goes with which function. SOH = Sine is Opposite over Hypotenuse. CAH = Cosine is Adjacent over Hypotenuse. TOA = Tangent is Opposite over Adjacent.

What is the formula for similarity in geometry? ›

The formula used to check if two triangles are similar or not depends on the condition of similarity. For two triangles △PQR and △XYZ , similarity can be proved using either of the following conditions, ∠P = ∠X, ∠Q = ∠Y and ∠R = ∠Z. PQ/XY = QR/YZ = PR/XZ.

What is the golden rule in geometry? ›

The golden ratio is found when a line is divided into two parts such that the whole length of the line divided by the long part of the line is also equal to the long part of the line divided by the short part of the line.

What is the SS rule in geometry? ›

SSS Criterion stands for Side-Side-Side congruence postulate. Under this criterion, if all the three sides of one triangle are equal to the three corresponding sides of another triangle, the two triangles are said to be congruent.

What are the 7 axioms? ›

AXIOMS
  • Things which are equal to the same thing are also equal to one another.
  • If equals be added to equals, the wholes are equal.
  • If equals be subtracted from equals, the remainders are equal.
  • Things which coincide with one another are equal to one another.
  • The whole is greater than the part.

What are the basic geometric principles? ›

The most basic geometric idea is a point, which has no dimensions. A point is simply a location on the plane. It is represented by a dot. Three points that don't lie in a straight line will determine a plane.

What are the rules of geometric patterns? ›

In geometric patterns the rule which makes the pattern is a sequence of moves that is repeated. In the example above the rule is “multiply the number by 2 and add 1.” The number pattern that results is: 4 9 19 38 … … … … We say that the number 19 is the third term in the pattern.

What is the general rule of the geometric series? ›

A geometric sequence is a sequence where the ratio r between successive terms is constant. The general term of a geometric sequence can be written in terms of its first term a1, common ratio r, and index n as follows: an=a1rn−1. A geometric series is the sum of the terms of a geometric sequence.

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