Basic triangle illustration and terminology

1. When performing trigonometry calculation, a reference angle is used. This is one of the
angles other than the 90 ° angle.
Opposite (O)
Reference angle (θ)
90° θ
Adjacent (A)
The triangle’s sides are determined by their relative location to the reference angle.
The side opposite the reference angle is the opposite (O).
The side adjacent to the reference angle is the adjacent (A).
The side opposite to the adjacent is the hypotenuse (H).