5.6.1: Key Terms
- Page ID
- 116119
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Key Terms
- adjacent side
- in a right triangle, the side between a given angle and the right angle
- angle
- the union of two rays having a common endpoint
- angle of depression
- the angle between the horizontal and the line from the object to the observer’s eye, assuming the object is positioned lower than the observer
- angle of elevation
- the angle between the horizontal and the line from the object to the observer’s eye, assuming the object is positioned higher than the observer
- angular speed
- the angle through which a rotating object travels in a unit of time
- arc length
- the length of the curve formed by an arc
- area of a sector
- area of a portion of a circle bordered by two radii and the intercepted arc; the fraction multiplied by the area of the entire circle
- cosecant
- the reciprocal of the sine function: on the unit circle,
- cosine function
- the x-value of the point on a unit circle corresponding to a given angle
- cotangent
- the reciprocal of the tangent function: on the unit circle,
- coterminal angles
- description of positive and negative angles in standard position sharing the same terminal side
- degree
- a unit of measure describing the size of an angle as one-360th of a full revolution of a circle
- hypotenuse
- the side of a right triangle opposite the right angle
- identities
- statements that are true for all values of the input on which they are defined
- initial side
- the side of an angle from which rotation begins
- linear speed
- the distance along a straight path a rotating object travels in a unit of time; determined by the arc length
- measure of an angle
- the amount of rotation from the initial side to the terminal side
- negative angle
- description of an angle measured clockwise from the positive x-axis
- opposite side
- in a right triangle, the side most distant from a given angle
- period
- the smallest interval of a repeating function such that
- positive angle
- description of an angle measured counterclockwise from the positive x-axis
- Pythagorean Identity
- a corollary of the Pythagorean Theorem stating that the square of the cosine of a given angle plus the square of the sine of that angle equals 1
- quadrantal angle
- an angle whose terminal side lies on an axis
- radian
- the measure of a central angle of a circle that intercepts an arc equal in length to the radius of that circle
- radian measure
- the ratio of the arc length formed by an angle divided by the radius of the circle
- ray
- one point on a line and all points extending in one direction from that point; one side of an angle
- reference angle
- the measure of the acute angle formed by the terminal side of the angle and the horizontal axis
- secant
- the reciprocal of the cosine function: on the unit circle,
- sine function
- the y-value of the point on a unit circle corresponding to a given angle
- standard position
- the position of an angle having the vertex at the origin and the initial side along the positive x-axis
- tangent
- the quotient of the sine and cosine: on the unit circle,
- terminal side
- the side of an angle at which rotation ends
- unit circle
- a circle with a center at and radius 1.
- vertex
- the common endpoint of two rays that form an angle

