# Trigonometry: Angles

### Terms

Angle  -  The union of two rays with a common vertex.
Coordinate Plane  -  Any plane with two perpendicular intersecting lines. The point of intersection of the lines is called the origin and the location of any point in the plane can be measured along the two lines, or axes.
Degree  -  A unit of measure for angles. 360 degrees equals one revolution and 2Π radians.
Initial Side  -  The side of an angle from which the rotation begins; the initial position of the ray whose rotation creates the angle.
Magnitude  -  The length of a vector
Minute  -  A subdivision of a degree. One minute is equal to degrees.
Ordered Pair  -  The \$x\$-coordinate and \$y\$-coordinate, placed together between parentheses and separated by a comma. An ordered pair specifies a location in the coordinate plane.
Origin  -  The intersection of the \$x\$-axis and \$y\$-axis in a coordinate plane. The location of the origin is (0,0).
Plot  -  To draw a point in the coordinate plane at a specific location. Points are plotted in the coordinate plane.
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. 2Π radians equals one revolution and 360 degrees.
Ray  -  A part of a line with a fixed endpoint on one end that extends without bound in the other direction.
Revolution  -  A rotation of the magnitude such that the initial side of an angle coincides with the terminal side; one complete rotation. One revolution equals 360 degrees and 2Π radians.
Second  -  A subdivision of a degree. One second is equal to degrees, or minutes.
Side  -  One of the rays that makes up an angle (is a side of the angle).
Standard Position  -  The location of an angle such that its vertex lies at the origin and its initial side lies along the positive \$x\$-axis.
Terminal Side  -  The side of an angle after rotation; the final position of the ray whose rotation created an angle.
Vector  -  A line segment with a starting point and an endpoint that represents motion in the direction of the endpoint, and which lies in a specific position such that its direction is fixed.
Vertex  -  The common endpoint of two rays that form an angle
x-axis  -  One of the two perpendicular lines that form the coordinate plane; usually the x-axis lies in a horizontal position.
x-component  -  The magnitude of a vector in the x direction.
x-coordinate  -  The distance between a point and the y-axis.
y-axis  -  One of the two perpendicular lines that form the coordinate plane; usually the y-axis lies in a vertical position.
y-component  -  The magnitude of a vector in the y direction.
y-coordinate  -  The distance between a point and the x-axis.

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