Common Core suggests: "Understand that by similarity, side ratios in right triangles are properties of the angles in the triangle, leading to definitions of trigonometric ratios for acute angles.".
Find Sin, Cos, Tan from Lengths of Triangle Sides - Expii
Right Triangle Trigonometry
Find Sin, Cos, Tan from Lengths of Triangle Sides - Expii
Trigonometric ratios the right triangle(in animation) – GeoGebra
Introduction to Right Triangle Trigonometry (Precalculus - Trigonometry 30)
Trigonometry: Tangent Identity - Expii
Find Measures of Angles Using Sin, Cos, Tan - Expii
Right Triangle Trigonometry - Basics of Right Triangle Trigonometry
Trigonometric Ratios - Definition, Formulas, Examples
Triangle Area in Terms of Base and Height - Expii
The Right Triangle Trig Functions (Clip)
How to Find Trigonometric Ratios Given a Right Triangle, Trigonometry
