As noted on the 'Intro' page, Trigonometry is based on ratios.
Comparing the lengths of two sides.
These three ratios are known as Sine, Cosine, and Tangent
Sine
Cosine
Tangent
"It's all about relationships' may seem to be an unusual quote for a Trigonometry unit, but it's true. Trigonometry is all about relationships.
Notice the triangles below. All the bases are congruent. The lengths of the opposite sides and the hypotenuses are all different because the reference angle is different:
Note that as the reference angle increases, the length of the opposite side increases. Essentially, a small angle is matched by a shorter opposite side length and a large angle is matched by a long opposite side length. Everything increases proportionally,