Take the right angle away and SOH CAH TOA has nothing to hold on to — there is no hypotenuse to be opposite or adjacent TO. What survives is a proportion that works in every triangle ever drawn: $\dfrac{a}{\sin A} = \dfrac{b}{\sin B} = \dfrac{c}{\sin C}$. Read it aloud: a over sine A equals b over sine B. Bigger angle, longer side facing it — the sine law is that intuition written down exactly.

The whole discipline is the PAIRING. Each side sits over the sine of the angle it faces across the triangle, never the angle it touches. Label your sketch with matching letters before you write a single fraction, and the two ways to slip — pairing a side with the wrong angle, or flipping the fraction — both disappear.

Two shapes trigger it: two angles and any side, or two sides and an angle facing one of them. One honest warning on that second shape — $\sin 150^\circ$ equals $\sin 30^\circ$, so a sine alone cannot tell an acute corner from an obtuse one. That is the ambiguous case, and it is why the drawings in this lesson say out loud that every corner is acute.