Definition:Cosine

Historical Note
The symbol $\cos$ was invented by in his 1657 work Trigonometrie.

Also see

 * Definition:Sine
 * Definition:Tangent Function
 * Definition:Cotangent
 * Definition:Secant
 * Definition:Cosecant


 * Definition:Hyperbolic Cosine


 * Properties of Cosine Function
 * Cosine of Complement equals Sine