The pre-calculus unit circle
In pre-calculus, the unit circle is sort of like unit streets, it’s the very small circle on a graph that encompasses the 0,0 coordinates. It has a radius of 1, hence the unit. The figure here shows all the measurements of the unit circle:
![The pre-calculus unit circle](https://www.dummies.com/wp-content/uploads/323183.image0.jpg)
Right triangles and trig functions for pre-calculus
If you’re studying pre-calculus, you’re going to encounter triangles, and certainly the Pythagorean theorem. The theorem and how it applies to special right triangles are set out here:
![image0.jpg](https://www.dummies.com/wp-content/uploads/323185.image0.jpg)
How to format interval notation in pre-calculus
In pre-calculus you deal with inequalities and you use interval notation to express the solution set to an inequality. The following formulas show how to format solution sets in interval notation.
![image0.png](https://www.dummies.com/wp-content/uploads/323187.image0.png)
Absolute value formulas for pre-calculus
Even though you’re involved with pre-calculus, you remember your old love, algebra, and that fact that absolute values then usually had two possible solutions. Now that you’re with pre-calculus, you realize that absolute values are a little trickier when you through inequalities into the mix. Never fear, the following formulas show you how to deal with absolute values in pre-calculus.
![Three absolute value formulas for pre-calculus.](https://www.dummies.com/wp-content/uploads/323189.image0.png)
Trig identities for pre-calculus
Of course you use trigonometry, commonly called trig, in pre-calculus. And you use trig identities as constants throughout an equation to help you solve problems. The always-true, never-changing trig identities are grouped by subject in the following lists:
![A list of trigonometry identities grouped by subject](https://www.dummies.com/wp-content/uploads/323191.image0.png)