1.1. Introduction to Sin, Cos and Tan

Sin (sine), cos (cosine) and tan (tangent) are the core three functions used in trigonometry and are based on a right-angled triangle.

“Opposite” is opposite to angle θ
”Adjacent” is adjacent to angle θ
”Hypotenuse” is the remaining side

They are each a measurement of ratio for the sides of a right angled triangle:

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

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

$\tan \theta =\frac{opposite}{adjacnet}$

because the calculation is a measure of ratio, size does not matter - only the angle is able to change the ratio.

These ratio operations can be remembered using the acronym SohCahToa:

Sine → opposite / hypotenuse
Cosine → adjacent / hypotenuse
Tangent → opposite / adjacent

Research Sources

1. https://www.mathsisfun.com/sine-cosine-tangent.html