Answer:
[tex]\boxed{\frac{1}{2}\pi}[/tex]
Step-by-step explanation:
Use length of arc formula.
[tex]\frac{\theta }{360} \times2 \pi r[/tex]
The radius is 1 unit.
θ = 90°
[tex]\frac{90}{360} \times 2\pi (1)[/tex]
[tex]\frac{1}{4} \times 2\pi[/tex]
[tex]\frac{1}{2} \times\pi[/tex]
