The mnemonic that pins all three trig ratios in your head.
Drag the corners
isosceles · acute
angles sum ≈ 180°
Drag a corner above to make a right triangle, then read off the sides. Label the side opposite your chosen angle, the hypotenuse (longest, opposite the right angle), and whatever's left is adjacent.
Your turn
Right triangle: adjacent = 4, opposite = 3 (so hypotenuse = 5). Find cos θ and tan θ.
Watch out
Mixing up 'opposite' and 'adjacent' — they're defined relative to the angle you're working with, not fixed to particular sides. Switch angles and they switch roles.
Decoded
- SOH — Sin = Opposite / Hypotenuse
- CAH — Cos = Adjacent / Hypotenuse
- TOA — Tan = Opposite / Adjacent
Try it
Right triangle, opposite=3, hypotenuse=5. Find sin θ.
sin θ = 3/5 = 0.6.