SOHCAHTOA — Sine, Cosine, Tangent
SOHCAHTOA is a memory aid: sin = opposite/hypotenuse, cos = adjacent/hypotenuse, tan = opposite/adjacent.
Choosing a ratio
From the acute angle you care about, label opposite, adjacent, and hypotenuse, then pick the ratio that uses the two sides you know or want.
Step-by-step method
- Mark the angle.
- Label opposite, adjacent, hypotenuse.
- Write the matching ratio and solve.
Example
sin(30°)
- Opposite/hypotenuse on a 30-60-90 triangle
- 1/2
Answer: 1/2
Interactive example
Solve a problem
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Example problems
Common mistakes
Labeling opposite from the wrong angle
Opposite is across from the angle you marked, not from the right angle.
Related formulas
Related calculators
Frequently asked questions
Does SOHCAHTOA work for obtuse angles?
The right-triangle story is for acute angles. Use the unit circle for general angles.