Trigonometry

Right angled triangles and Phythagoras’ Theorem

c² = a² + b²

• So:
  • c = √a² + b²
  • a = √c² + b²
  • b = √c² + a²

Right angled triangles and the Trigonometric ratios

• Sin A = opposite/hypotenuse

• Cos A = adjacent/hypotenuse

• Tan A = opposite/adjacent

• / means over

  

• Opposite = The side opposite the acute angle

• Hypotenuse = side opposite right angle

• Adjacent = the remaining side beside the acute angle

Finding angles

Example:

1. Sin A = opposite/hypotenuse so Sin A = 3/7
2. Put Sin^-1(3/7) into the calculator to get 25.37.. which rounds to 25 degrees
3. A = 25 degrees