Like a square wave, the triangle wave contains only odd harmonics. However, the higher harmonics roll off much faster than in a square wave (proportional to the inverse square of the harmonic number as opposed to just the inverse).
For example, for a triangle wave with amplitude 5 and period 4:
A phase shift can be obtained by altering the value of the term, and the vertical offset can be adjusted by altering the value of the term.
As this only uses the modulo operation and absolute value, it can be used to simply implement a triangle wave on hardware electronics.
It is possible to approximate a triangle wave with additive synthesis by summing odd harmonics of the fundamental while multiplying every other odd harmonic by −1 (or, equivalently, changing its phase by π) and multiplying the amplitude of the harmonics by one over the square of their mode number, n (which is equivalent to one over the square of their relative frequency to the fundamental).
The above can be summarised mathematically as follows:
where N is the number of harmonics to include in the approximation, t is the independent variable (e.g. time for sound waves), is the fundamental frequency, and i is the harmonic label which is related to its mode number by .
This infinite Fourier series converges quickly to the triangle wave as N tends to infinity, as shown in the animation.