A first way is considering opposite angles:
- Pick a point,
- Draw two rays
starting from
- Let
be the angle between
and
- Elongate both
with respect to
to obtain the rays
and
- The angle between
is also
Alternatively, you can start with a given angle, and then draw its bisector. By definition, the bisector cuts a given angle in two equal parts, so you divide an angle in two parts, both measuring