Terms
Amplitude

Onehalf the distance between the minimun and maximum value of a periodic
function.
Coterminal

Having the same terminal side (a property of angles).
Identity

An equation containing one or more trigonometric functions which are true
regardless of the angle used.
Initial Side

The side of an angle from which the rotation begins, or the initial position of
the ray whose rotation creates the angle.
Inverse Trigonometric Function

The inverses of the six trigononometric
functions with specific restricted ranges. They are arcsine,
arccosine, arctangent, arccosecant, arcsecant, and
arccotangent.
Period

The repeating interval of a periodic function;
the period of a function is a real number.
Quadrant

One of the four regions in the coordinate plane created by the intersection of
the axes.
Quadrantal Angle

An angle in standard position whose terminal side lies along one of the
axes.
Radian

A unit of measure for angles. One revolution equals 2Π radians. A radian
is also the measure of the central angle that intercepts an arc of the same
length as the radius.
Reference Angle

The positive acute angle formed between the terminal side of an angle and
the xaxis.
Standard Position

The location of an angle such that its vertex lies at the origin and its
initial side lies along the positive xaxis.
Terminal Side

The side of an angle after rotation; the final position of the ray whose
rotation created an angle.
Trigonometric Functions

Sine, cosine, tangent, cosecant, secant, and cotangent
are the six trigonometric functions.
Vertex

The common endpoint of two rays that form an angle.
arccosecant
 y = arccsc(x) = csc^{1}(x). Another way to write x = csc(y).

arccosine
 y = arccos(x) = cos^{1}(x). Another way to write x = cos(y).

arccotangent
 y = arccot(x) = cot^{1}(x). Another way to write x = cot(y).

arcsecant
 y = arcsec(x) = sec^{1}(x). Another way to write x = sec(y).

arcsine
 y = arcsin(x) = sin^{1}(x). Another way to write x = sin(y).

arctangent
 y = arctan(x) = tan^{1}(x). Another way to write x = tan(y).

Cosecant

Given a point P(x, y) on the terminal side of an angle θ in
standard position, distance d from the origin, its cosecant is
csc(θ) = = .

Cosine

Given a point P(x, y) on the terminal side of an angle θ in
standard position distance d from the origin, its cosine is cos(θ) = .

Cotangent

Given a point P(x, y) on the terminal side of an angle θ in
standard position, its cotangent is cot(θ) = = .

Secant

Given a point P(x, y) on the terminal side of an angle θ in
standard position, distance d from the origin, its secant is sec(θ) = = .

Sine

Given a point P(x, y) on the terminal side of an angle θ in
standard position, distance d from the origin, its sine is sin(θ) = .

Tangent

Given a point P(x, y) on the terminal side of an angle θ in
standard position, its tangent is tan(θ) = = .
