sohcahtoa

Let $\theta$ be an acute angle and fix a right triangle having $\theta$ as one of its angles. The trigonometric functions $\sin \theta$, $\cos \theta$, and $\tan \theta$ can be defined as:

$$\sin \theta =\frac{\text{opposite}}{\text{hypotenuse}}$$

$$\cos \theta =\frac{\text{adjacent}}{\text{hypotenuse}}$$

$$\tan \theta =\frac{\text{opposite}}{\text{adjacent}}$$

A mnemonic device for remembering the three given above is sohcahtoa.

The sohcahtoa can be divided up into three portions of three letters each. The first portion, soh, should recall to memory that $\sin \theta$ is opposite over hypotenuse; the second portion, cah, should recall to memory that $\cos \theta$ is adjacent over hypotenuse; and the third portion, toa, should recall to memory that $\tan \theta$ is opposite over adjacent.

I would like to thank Mrs. Sue Millikin for teaching me trigonometric functions using this mnemonic device.