Triangle law of vector additionstates that when twovectorsare represented by two sides of atrianglein magnitude and direction taken in same order then third side of thattrianglerepresents in magnitude and direction the resultant of thevectors.

This simply means that, if you have a two vectors that represents the two sides of the triangle then the third side of that triangle will represent their resultant.

Example

In a time of one period, the wave has moved a distance of one wavelength. Combining this information with the equation for speed (speed = distance/time), it can be said that the speed of a wave is also the wavelength/periodsSince the period is the reciprocal of the frequency, the expression 1/f can be substituted into the above equation for period. Rearranging the equation yields a new equation of the form:

Speed =Wavelength×Frequency

The above equation is known as the wave equation. It states the mathematical relationship between the speed (v) of a wave and its wavelength (λ) and frequency (f). Using the symbolsv, λ, andf, theequation can be written as v=f×λ