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Useful Facts and Formulas
Useful Facts and Formulas
9
Mathematics
7th Grade
11/10/2025

Additional Mathematics Flashcards

 


 

Cards

Term

Arithmetic Series

(Sum of the numbers in an Arithmetic Sequence)

Definition

 

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or 

 

 

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Term
Difference of Squares
Definition
a2 - b2 = (a+b)*(a-b)
Term
Pythagorean Theorem
Definition
a2 + b2 = c2
Term

Geometric Sequence

 

(sum of geometric series)

Definition

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Sum of an infinite geometric series where

-1<r<1

 

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Term
Sides of a 30-60-90 triangle
Definition

leg 1 = a,
leg 2 = a√3
hypotenuse = 2a

 

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Term
Sides of a 45-45-90
Definition

leg 1 = b
leg 2 = b
hypotenuse = b√2

 

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Term
Area of a Triangle
(Heron’s formula)
Definition

semiperimeter = s = (a + b + c)/2

 

 

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Term
Complementary Angles
Definition

Two angles that add up to 90 degrees

In a right triangle, the two non-right angles are complementary.

To help remember: “C” of Complementary is for “Corner” right angle (a Right Angle)

Term
Supplementary Angles
Definition

Two angles that add up to 180 degrees

To remember: “S” of Supplementary is for “Straight” (180° is a straight line)

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