Geometry Formulas and Definitions

A = πr²

A = L x W

A = (B× H) ÷ 2

V = π/4 x D^2 x H

V = L× W×H

The root of a number is one of two or more equal numbers that, when multiplied together, will produce the number.

A figure formed by two lines radiating from a common point.

An angle of 90°.

An angle greater than 90° but less than a straight line.

An angle between 0° and 90°.

One fourth of a circle.

The portion of a circle bounded by two radii and one of the intercepted arcs.

A closed figure having three or more sides.

A triangle with three acute angles.

A triangle with one obtuse angle.

A triangle containing a 90° angle.

A triangle with three equal sides.

A triangle with two equal sides.

A triangle in which no two sides are equal.

The side opposite the right angle.

A polygon having four sides.

A closed four-sided figure in which the opposite sides are parallel.

A closed four-sided figure in which only one pair of opposite sides are parallel.

A closed figure with six equal sides.

Pi (r) is the constant amount the circumference of a circle is greater than its diameter.

п = 3.1416

A fraction that compares one number to another; for example, 6:2 is a ratio.

A statement of equality between two ratios; for example, a=b/c

A fraction having 100 as the denominator. For example: 65%

64

9,801

125

10

189.3 liters.

55 pounds.

10

3

A method of writing very large or very small numbers using powers of 10.

When converting standard notation to scientific notation, move the decimal to the left or right until there is one non-zero integer on its left. If you moved the decimal to the left, you'll multiply by ten times the number you moved it to the left, so 56,000,000 would be 5.6 × 107.

9.6 × 10-7

57,400

3.142

256

The metric system.

A number less than 0, or a number preceded by a minus (-) sign.

Add all numbers having a plus sign, add all numbers having a minus sign, of all of these answers subtract the smaller from the larger number. The sign of the answer will be the sign of the larger number.

1. Change the sign of the subtrahend (the number that is being subtracted). 2. If the signs are alike, add the two numbers and attach the common sign. 3. If the signs are different, subtract the smaller from the larger and give the answer the sign of the larger.

1. Multiply the numbers, disregarding the signs. 2. If the signs of the two numbers are alike, the sign of the answer is positive. 3. If the signs of the two numbers are not alike, the sign of the answer is negative.

1. Disregard the signs and divide as though the numbers had no signs. 2. If the signs of the two numbers are alike, the sign of the answer is positive. 3. If the signs of the two numbers are not alike, the sign of the answer is negative.

1. Grouped expressions, such as parenthesis and radical expressions (square roots) 2. Exponents 3. Multiplication and division 4. Addition and subtraction

18

-6

-6

-18

6

72

-72

-1/2

1/2

Incorrectly solving algebraic equations can have serious consequences. One example is incorrectly computing the center of gravity (CG) after weighing an aircraft. An incorrectly computed CG could lead to a catastrophic outcome if the aircraft is loaded outside of the actual allowable limits.

When installing and removing equipment from an airplane, it is important that the calculations are correct. Components may be either ahead or behind the datum and thus the moments can be either positive or negative. Incorrectly applying the rules of positive and negative integers will cause the stated weight and balance of the airplane to be incorrect.

Rounding off calculations too far or incorrectly can lead to many dangerous situations. This can result in replacement wires that are too small, switches and circuit breakers that are not rated sufficiently for the load of the circuit, incorrectly sized alternators, and many other dangerous situations.