Topics in a Trigonometry Course

To learn more about a topic listed below, click the topic name to go to the corresponding MathWorld classroom page.

Cosine	The cosine is the ratio of the length of an angle's adjacent side to the length of the hypotenuse in a right triangle.
Double-Angle Formulas	The double-angle formulas are a set of formulas that express trigonometric functions of twice an angle in terms of the trigonometric functions of the original angle.
Half-Angle Formulas	A set of formulas that express trigonometric functions of half an angle in terms of the trigonometric functions of the original angle.
Law of Cosines	The law of cosines is a formula relating the side lengths and angles of a general triangle which is a generalization of the Pythagorean theorem.
Law of Sines	The law of sines is a formula relating the ratios of sines of angles to the opposite side lengths for a general triangle.
Sine	The sine is the ratio of the length of a given angle's opposite side to the length of the hypotenuse in a right triangle.
Tangent	(1) In trigonometry, the tangent of an angle is the ratio of the length of a given angle's opposite side to the length of the angle's adjacent side in a right triangle. (2) In geometry, two figures are said to be tangent to one another if they "just touch".
Trigonometric Addition Formulas	The trigonometric addition formulas are a set of formulas that express trigonometric functions of sums of angles in terms of the trigonometric functions of the original angles.
Trigonometry	Trigonometry is the study of angles and of the angular relationships of planar and three-dimensional figures.
Unit Circle	The unit circle is a circle of radius one.