SOH-CAH-TOA, the ratios it names, and the circle that carries them past the right triangle.
The answer key prints on a separate page.
Sine, cosine, and tangent are ratios of sides, and the whole of right-triangle trig is choosing the right one for what you know and what you want. SOH-CAH-TOA is the mnemonic, but the reliable error is upstream of it: labeling the opposite and adjacent sides relative to the wrong angle, so the correct ratio is applied to the wrong pair. The first two sections separate naming the ratio from using it for exactly that reason.
Identities and the unit circle are where trig stops being about a single triangle. An identity like sin²θ + cos²θ = 1 is the Pythagorean theorem in disguise, true for every angle, and the unit circle is what lets a ratio mean something for angles a right triangle cannot hold. A child fluent with SOH-CAH-TOA and lost on the unit circle has the tool and not yet the setting it generalizes to.
