To determine which construction can be used to construct an angle whose measure is equal to [tex]\( \frac{2m\angle CAB}{2} \)[/tex], let's analyze each of the given options.
Given that the answer is 4 degrees, this implies [tex]\( 2m\angle CAB = 4 \)[/tex]. Therefore:
[tex]\[ m\angle CAB = 2 \][/tex]
1. Bisect [tex]\(\angle CAB\)[/tex]:
- If you bisect [tex]\(\angle CAB\)[/tex], you are cutting the angle in half to create two equal angles.
- This would result in two angles of [tex]\( \frac{m\angle CAB}{2} \)[/tex].
2. Copy [tex]\(\angle CAB\)[/tex] on AC:
- Copying the angle [tex]\(\angle CAB\)[/tex] means creating another angle [tex]\(\angle BAC\)[/tex] that is exactly the same size as [tex]\(\angle CAB\)[/tex].
- This does not change the measure of the angle but replicates it.
3. Copy AC:
- Copying the segment AC does not affect or change the angle [tex]\(\angle CAB\)[/tex].
4. None of the above:
- This option suggests that none of the previous methods can achieve constructing an angle whose measure is [tex]\( 2m\angle CAB \)[/tex].
Given the provided numerical answer is [tex]\(4\)[/tex], it is evident that to achieve this we need to bisect an angle of 4 degrees. Hence, the correct construction is option:
A. Bisect [tex]\(\angle CAB\)[/tex]
