# Trigonometric Ratios: sine, cosine and tangent

Given the right triangle $$ABC$$, we define the sine, the cosine and the tangent of an angle $$x$$ as:

1. $$\sin(x)$$: the sine of the angle $$x$$ is the ratio between the opposite cathetus and the hypotenuse: $$\sin(x)=\dfrac{a}{c}$$$2. $$\cos(x)$$: the cosine is the ratio between the adjoining cathetus and the hypotenuse: $$\cos(x)=\dfrac{b}{c}$$$

3. $$\tan(x)$$: the tangent is defined as the ratio between the opposite cathetus and the adjoining one: $$\tan(x)=\dfrac{a}{b}$$\$