25.1.2 Defining Sine, Cosine, and Tangent
Core ideaFix an angle in a right triangle and the proportions of its sides are locked in, so we give those three ratios names: sinA, cosA, and tanA.
Module goal. Carrying the function idea forward, we first build the link between an angle and the ratios of sides inside the most familiar shape — the right triangle — and learn to use it to measure real heights and distances.