Term | Definition |
Radians | A unit of angle, equal to an angle at the center of a circle whose arc is equal in length to the radius. |
Degrees | A unit of measurement of angles, one three-hundred-and-sixtieth of the circumference of a circle: "set at an angle of 45 degrees". |
Coterminal Angle | Two angles are coterminal if they are drawn in the standard position and both have their terminal sides in the same location. |
Quadrantal angle | An angle with terminal side on the x-axis or y-axis. That is, the angles 0°, 90°, 180°, 270°, 360°, 450°, ... as well as –90°, –180°, –270°, –360°, ... |
Unit Cicle | The circle with radius 1 which is centered at the origin on the x-y plane. |
Reference angle | Is an acute version of that angle |
Sine | Written sin θ, Opposite/hypontenuse |
Cosine | For acute angles, cos θ, Adjacent/hypotenuse |
Tangent | tan θ equals Sinθ/Cosθ |
Cosecant | The ratio of the hypotenuse (in a right-angled triangle) to the side opposite an acute angle; the reciprocal of sine |
Secant | The ratio of the hypotenuse to the shorter side adjacent to an acute angle (in a right-angled triangle); the reciprocal of a cosine. |
Cotangent | The ratio of the side (other than the hypotenuse) adjacent to a particular acute angle to the side opposite. |
Inverse | The quantity which cancels out the a given quantity |
Arcsin | The inverse function of the sine; the angle that has a sine equal to a given number. |
Arccos | The inverse function of the cosine; the angle that has a cosine equal to a given number. |
Arctan | The inverse function of the tangent; the angle that has a tangent equal to a given number. |
Law of Sines | Equations relating the sines of the interior angles of a triangle and the corresponding opposite sides. |
Law of Cosines | An equation relating the cosine of an interior angle and the lengths of the sides of a triangle. |