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Trigonometry Reference


A right triangle is defined as having one angle precisely equal to 90o (a right angle).

Trigonometric identities

Trigonometric identities

Hypotenuse Opposite Adjacent

H is the Hypotenuse, always being opposite the right angle. Relative to angle x, O is the Opposite and A is the Adjacent.

"Arc" functions such as "arcsin", "arccos", and "arctan" are the complements of normal trigonometric functions. These functions return an angle for a ratio input. For example, if the tangent of 45o is equal to 1, then the "arctangent" (arctan) of 1 is 45o. "Arc" functions are useful for finding angles in a right triangle if the side lengths are known.

The Pythagorean theorem

Pythagorean Theorem

The Law of Sines (for any triangle)

Law of sines Sines, law of

The Law of Cosines (for any triangle)

Law of cosines Cosines, law of

Trigonometric equivalencies

Hyperbolic functions Radian Unit, radian

Note: all angles (x) must be expressed in units of radians for these hyperbolic functions. There are 2π radians in a circle (360o).

Contributors to this chapter are listed in chronological order of their contributions, from most recent to first. See Appendix 2 (Contributor List) for dates and contact information.

Harvey Lew (??? 2003): Corrected typographical error: "tangent" should have been "cotangent".

Last Update: 2010-12-01