A chord separates the circumference ... 90° is one quarter of the whole circle (360°). The arc length is \(\frac{1}{4}\) of the full circumference. Remember the circumference of a circle ...

A chord separates the ... what fraction of the whole circle we have. 90° is one quarter of the whole circle (360°). Therefore, the arc length is \(\frac{1}{4}\) of the full circumference.