Consider a right triangle *BAC*:

Hypotenuse: , m () = a.

Catetos: , m () = b.

, m () = c.

Angles: , and .

Based on the elements of this triangle, we can define the following trigonometric ratios:

**Sine**of an acute angle is the ratio between the measurement of the opposite side of that angle and the hypotenuse.

Like this:

**Cosine**of an acute angle is the ratio between the measurement of the adjacent pallet to this angle and the measurement of hypotenuse.

Like this:

Next: Tangent