What is the origin of sine, cosine, tangent, secant, cosecant, cotangent?

1 Answer
Nghi N.
Jul 3, 2015

Definition of trig functions

Explanation:

The 4 trig functions sin x, cos x, tan x and cot x are called circular functions. They are the projections of an arc x, that rotates counterclockwise on the trig unit circle, on 4 different axis of the trig circle.
On the trig unit circle,
The horizontal axis OAx defines the function f(x) = cos x
The vertical axis OBy defines the function f(x) = sin x
The vertical axis AT defines the function f(x) = tan x
The horizontal axis BU defines the finction f(x) = cot x
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