00:01
So in this problem we have two waves that are identical but they are going in opposite directions because their velocities are oriented in opposite directions.
00:11
So one is going into positive horizontal direction and another is going in the negative horizontal direction therefore, we can say that the wave function of one of them y1 is going to be a the amplitude sinus and k x minus omega t so this is corresponding to the positive horizontal direction and for the negative horizontal direction the wave function is the same exact same waves are exactly the same but the sign is will be kx plus omega t so what happens when we want to add these two together we need to remind ourselves that there is a trigonomic formula which states that anytime we want to we have sinus of two angles, for example alpha and beta, this can be, this is equal to sinus for alpha, cosynes, beta plus cosinus, alpha, sinus beta.
01:27
In this case we have, this will be our alpha angle and this will be our beta angle.
01:35
And we will use this formula two times.
01:43
So, y1 plus y2 will be equal, and now we can always move altitude in front of the brackets because it is a common multiplicator and it multiplies, it multiplies.
02:07
So we will start with sinus off.
02:11
We will immediately expand the functions.
02:14
So, sinus of kx, we said this is our alpha angle times cosine of omega -t, this is our bit angle.
02:25
And we continue in this manner for both functions and their terms...