SL 3.4—Arc length and sector area

At SL, an angle $\theta$ in degrees selects the fraction $\theta/360$ of a full circle. Therefore arc length is $s=(\theta/360)(2\pi r)$ and sector area is $A=(\theta/360)(\pi r^2)$.

Use the radius, not the diameter, and keep the angle in degrees. A perimeter of a sector includes the curved arc plus two radii, while the area formula includes only the sector region.

Example

For $r=6$ cm and $\theta=120^\circ$, $s=(120/360)(12\pi)=4\pi$ cm and $A=(120/360)(36\pi)=12\pi$ cm$^2$. The sector perimeter is $12+4\pi$ cm.

Radians are not required at SL. Do not use $s=r\theta$ unless $\theta$ is in radians, and do not report area in linear units.