Your goal in this example is to linearize the functional model for an angle measured between two points.
We considered the measurement of azimuth in detail in Example 8, i.e. an angle measured at a point between north and a second point .
Now I want you to consider the case of an angle measured at a point between any two points and . Because this can be viewed as a simple difference of azimuths, I will leave the sketch to you.
I want you to derive the linearized functional model for such an angle, and represent it as .
Do provide a sketch and show your work, but because it follows so closely from Example 8, feel free to reference (bring in) the results from that example without re-doing them.