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) = 30o