# Math

## Featured Videos

### How to Add and Subtract Fractions in Algebra (Video)

In algebra, adding and subtracting fractions is easy when you find the common denominator. This video shows you how to convert fractions for the common denominator. After you determine the common denominator, you can add and subtract fractions, including story problems, with ease.

### How to Find the Volume of a Solid with a Circular Cross-Section (Video)

Calculus allows you to calculate the volume of conical objects by dividing the object into an infinite number of circular cross-sections - geometrical shapes resembling pancakes or washers - and adding up the volume of all those cross-sections through integration. This video tutorial shows you how.

## Most Popular

### Mastering the Formal Geometry Proof

Suppose you need to solve a crime mystery. You survey the crime scene, gather the facts, and write them down in your memo pad. To solve the crime, you take the known facts and, step by step, show who committed

### Sizing Up the Area of a Polygon

Not only can polygons be classified by the number of sides they have and by their angles, but they can also be grouped according to some of their qualities. Polygons can have three personality characteristics

### Simple and Easy Geometry Tips and Tools

The first rule of life? Life (as well as geometry) can be difficult. But why make it more difficult than it has to be? Do you need help with geometry? Here are 11 tried-and-true tips to make your forays

### Measuring and Making Angles

On a map, you trace your route and come to a fork in the road. Two diverging roads split from a common point and form an angle. The point at which the roads diverge is the

### Classifying Three Types of Triangles

Triangles are classified according to the length of their sides or the measure of their angles. These classifications come in threes, just like the sides and angles themselves. That is, a triangle has

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### Algebra's Rules of Divisibility

In algebra, knowing the rules of divisibility can help you solve faster. When factoring algebraic expressions to solve equations, you need to be able to pull out the greatest factor. You also need common

### Algebra I For Dummies Cheat Sheet

Algebra problems are easier to solve when you know the rules and formulas. Memorizing key algebra formulas will speed up your work, too. And if you know the rules of divisibility and the order of operations

### Mathematical Order of Operations

The rules for deciding the order to evaluate arithmetic expressions, no matter how complex, are called the order of operations. The complete order of operations in math are:

### Mathematical Inequalities

When two numbers are different in value, a variety of symbols are used to turn them into an inequality. The four most common inequalities in arithmetic are:

### Mathematical Place Value

Our number system (Hindu-Arabic) has ten familiar digits, 0 to 9. Numbers higher than 9 are made using place value, which assigns a digit a greater or lesser value depending on where it shows up in a number

### Understanding Absolute Value and Negation

The positive value of a number is its absolute value. It tells you the distance of a number from zero on the number line. Placing bars (| |) around a number or expression gives you its absolute value:

### Basic Algebra Conventions

In algebra, a letter such as x that takes the place of a number in one or more equations is called a variable. Practices you need to know about how algebra problems are written:

### Solving an Algebraic Equation

An algebraic equation is an equation with at least one variable. Apply operations equally to both sides to modify an equation. For example, you can add 2 to both sides, subtract x from both sides or multiply

### Basic Math & Pre-Algebra Workbook For Dummies Cheat Sheet

To successfully study pre-algebra, understand that a specific order of operations needs to be applied. Also recognize some basic math principles, such as the ability to recognize and understand mathematical

### How to Find Higher Math Functions on the TI-89 Graphing Calculator

Of course, your TI-89 graphing calculator helps you with higher math functions — that’s part of the reason you bought it. However, you might need help finding everything. The following list doesn’t tell

### How to Format Equations on the TI-89 Graphing Calculator

Your TI-89 graphing calculator can help you solve equations and systems of equations. All you have to do is put them in the proper format. Fortunately, the following list shows how to format equations

### Special Keys on the TI-89 Graphing Calculator

The TI-89 graphing calculator has so many functions, you may have trouble locating them all. But if you’re looking for theta or infinity (and who isn’t, right?), look no further than the following list

### Basic Keystrokes on the TI-92 and Voyage 200 Graphing Calculators

The TI-89, TI-92, and Voyage 200 calculators have similar functions, but in the case of the TI-92 and Voyage 200, different ways of accessing them. The following list shows how to access some basic functions

### How to Access Symbols on the TI-89 Graphing Calculator

Of course your calculator needs a not-equal-to sign, but the TI-89 graphing calculator also offers the @, an exclamation mark, and a sigma. The following list shows you how to produce these symbols and

### Accessing Odd Functions on the TI-89 Graphing Calculator

The TI-89 graphing calculator has all kinds of special functions. It can, of course, give you the mathematically certain answer you need, but it can also offer an approximation. You can tell it to stop

### How to Find a Normal Line Perpendicular to a Tangent Line

A line normal to a curve at a given point is the line perpendicular to the line that’s tangent at that same point. Find the points of perpendicularity for all normal lines to the parabola

### How to Approximate Area with Left Sums

You can approximate the area under a curve by using left sums. For example, say you want the exact area under a curve between two points, 0 and 3. The shaded area on the left graph in the below figure

### How to Approximate Area with Right Sums

You can approximate the area under a curve by using right sums. This method works just like the left sum method except that each rectangle is drawn so that its right upper corner touches the curve instead

### How to Approximate Area with the Trapezoid Rule

With the trapezoid rule, instead of approximating area by using rectangles (for example, as you do with the left and right sum methods), you approximate area with — can you guess? — trapezoids.

### How to Do Simple Integration by Parts

Integrating by parts is the integration version of the product rule for differentiation. The basic idea of integration by parts is to transform an integral you

### How to Change Unacceptable Forms before Using L'Hôpital’s Rule

You can use L'Hôpital’s rule to find a limit for which direct substitution doesn't work. If substitution produces one of the unacceptable forms, ± ∞ · 0 or ∞ – ∞, you first have to tweak the problem to

### How to Use Tangent Substitution to Integrate

With the trigonometric substitution method, you can do integrals containing radicals of the following forms:

### How to Use Sine Substitution to Integrate

With the trigonometric substitution method, you can do integrals containing radicals of certain forms because they match up with trigonometric functions. A sine can take the place of a radical in a particular

### How to Find the Average Value with the Mean Value Theorem for Integrals

You can find the average value of a function over a closed interval by using the mean value theorem for integrals. The best way to understand the mean value theorem for integrals is with a diagram — look

### How to Find the Volume of a Complicated Shape with the Meat-Slicer Method

You can use the meat-slicer method to determine the total volume of a complicated shape. In geometry, you learned how to figure the volumes of simple solids like boxes, cylinders, and spheres. Integration