The world can be converted into triangles.
All shapes can be broken down into triangles. (Anything else that would need an arc comes from circles, which is also in Trig but that will be another discussion)
When we say the cos(angle), we mean that we want to "do" cosine, to that angle.
What does that mean?
Well, it is kinda like if I said (angle)^2
It means we are doing something to that angle.
Now, if I tell you that X * Y = Z
Then I tell you X and Z are equal to 5 and 10, you could easily figure out that Y = 2.
Trig is the same way.
There is a triangle.
/*
I should clarify, it is a RIGHT triangle, meaning there is a 90 degree angle. all shapes can be broken down into right triangles and/or circles
*/
With the information of A, B, C, and either of the angles that is not the 90, I can find out the rest of the info.
So when it is said that:
sine = opposite / hypotenuse
That means that the sin of an angle is equal to the opposite side,, A would be opposite in that picture,, divided by the hypotenuse ,,that would be C, or the longest side on the triangle.
So it is the same as saying X * Y = Z
Sin(angle) = OppositeSide / Hypotenuse
So now if we have both sides, we can find the angle.
If we have one side and one angle, we can find the other side.
With all of the trig functions, sine, cosine, tangent, secant, cosecant, cotangent, we can use them to find any piece of the triangle based on any 2 other pieces.
So having the Yaw, which is the angle, if u have an distance, or height, or whatever becomes the other piece of the triangle, you can figure out the rest.
It is hard to explain over the internet...