**Angle:**

An angle consists of two rays, R1 and R2, with a common vertex.

**Standard position of an angle:**

An angle is said to be in standard position if its vertex is at the origin of a rectangular coordinate system and its initial side coincides with the positive x-axis.

**Co-terminal angles:**

Two angles in standard position are said to be co-terminal if they have the same initial and terminal sides.

**Arc length:**

For a circle of radius , a central angle of radius subtends and arc whose length is

.

is measured in radians.

**Area of a sector:**

The area of the sector of a circle of radius formed by a central angle radians is

where the unit of angle must be in radians.

**Linear speed:** The linear speed is defined as .

**Angular speed: **The angular speed is defined as . ** **

**The domain of the sine function:**

The domain of the sine function is the set of all real numbers.

**The domain of the cosine function:**

The domain of the cosine function is the set of all real numbers.

** **

**Periodic function:**

A function is called periodic if there is a positive number such that, whenever is in the domain of so is and . P is the period of

**The Period of sine and cosine functions:**

The period of sine and cosine functions is