The document discusses trigonometric functions, arcs, sectors, and related concepts. It defines:
- 360° = 2π radians
- The circumference of a circle is given by C = 2πr
- The area of a circle is given by A = πr^2
- The length of an arc is given by l = rθ
- The area of a sector is given by A = (1/2)r^2θ
It provides an example calculating the length of an arc and area of a sector for a circle with radius 5cm and central angle of 45°.