Trigonometry
Trigonometry seeks to find the lengths of a triangle's sides, given 2 angles and a side. Trigonometry is closely related to analytic geometry.
Contents
[hide]Basic definitions
Usually we call an angle , read "theta", but
is just a variable. We could just as well call it
.
image
Sine
The sine of an angle , abbreviated
, is the ratio between the base and the hypotenuse of a triangle with the uppermost angle equal to theta. For instance, in the 30-60-90 triangle above,
.
Cosine
The cosine of an angle , abbreviated
, is the ratio between the altitude and the hypotenuse of a triangle with the uppermost angle equal to theta. For instance, in the 30-60-90 triangle above,
.
Tangent
The tangent of an angle , abbreviated
, is the ratio between the base and altitude of a triangle with the uppermost angle equal to theta. For instance, in the 30-60-90 triangle above,
. (Note that
.)