What are the trigonometric functions?

The main three trigonometric functions are the tangent (tan), sine (sin) and cosine (cos) functions. The tangent, sine and cosine of an angle is defined in terms of the ratios of the length of sides of a right-angled triangle - i.e. number you get when you divide the length of a specific side by the length of another specific side. The easy way to remember which sides to divide to get the tan/sin/cos of an angle is SOH CAH TOA where the first letter stands for the trig function (S:sin, C:cos, T:tan) the second is the numerator of the fraction where O stands for the length of the opposite side of the triangle A stands for the adjacent and H stands for the hypotenuse, the last letter is the denominator of the fraction created. For example SOH means that if we want to find the sine of an angle A this is given by sinA = (Length of opposite side)/(Length of hypotenuse). The trigonometric functions have a lot of very useful properties which is why we study them. That they can be used to calculate the unknown lengths of sides in right angled triangles is but one their uses.