We can find an unknown angle in a right-angled triangle, as long as we know the lengths of two of its sides.

Use Sine, Cosine or Tangent!

Use ** SOHCAHTOA **to help you, like this:

Table of Contents

## How to Finding an Angle in a Right Angled Triangle

**1. find the names of the two sides we know**

- Adjacent is adjacent to the angle,
- Opposite is opposite the angle,
- Hypotenuse is The longest side.

**2. Find which one of Sine, Cosine or Tangent to use:**

**SOH**… Sine: sin(θ) = Opposite / Hypotenuse

…**CAH**… Cosine: cos(θ) = Adjacent / Hypotenuse

…**TOA** Tangent: tan(θ) = Opposite / Adjacent

**3. Put the values into equation **

**4. Solve that equation and find the value of θ**

## Example

Sin (θ) = Opposite / Hypotenuse = 3 / 6 = 0.5

Sin (θ) = 0.5,

then θ = sin^{-1}(0.5) = 30^{o}