What even is trigonometry?

As we saw earlier in the special cases section, all right triangles have specific ratios between their angles and their lengths. For the special cases, the ratios are easy to remember, but when the angles are different, we use trigonometric functions to figure out the lengths of sides and angles without doing a lot of steps of math. Yay!

Vocabulary to Know

• Adjacent – the side next to the angle
• Opposite – the side across from the angle
• Hypotenuse – the longest side across from the right angle

SOH CAH TOA

This is a way to remember which trig function goes with which sides of a triangle:

Sin(x) is a function that describes the ratio of the side opposite an angle (x) to the hypotenuse.

Cos(x) is a function that describes the ratio of the side adjacent to an angle (x) to the hypotenuse.

Tan(x) is a function that describes the ratio of the side opposite an angle (x) to the side adjacent to the angle.

In Algebra 2, you’ll learn more about what these functions look like and how they work, but right now all you need to know is the sides of a triangle they apply to!