Interestingly enough, the trigonometric functions that define those relationships are also closely tied to circles. Needless to say, this makes trig one of the hardest topics in math for students ...

Solve trigonometric equations in Higher Maths using the double angle formulae, wave function, addition formulae and trig identities.

Both the sine and cosine functions have outputs between -1 and 1 (because the x and y values can be negative). You can think of these trig functions as a sort of "lookup table." ...