Here I made a triangle where A is the first sighting, B is the light, and C is the second sighting.
The question is, what is the length of BC ?
On this first one, I just focused on the angles.
m∠BAC = 107º - 60º = 47º
measure of the green angle = 180º - 107º = 73º
Since the two vertical lines are parallel and line AC crosses them, we have two parallel lines cut by a transversal. So.. the two green angles are the same.
Now let's just look at the second triangle.
We can use law of sines to find BC.
\(\frac{1.5}{\sin 26}=\frac{BC}{\sin 47} \\~\\ \frac{1.5}{\sin 26}*\sin 47 =BC \\~\\ 2.503\text{ km} \approx BC\)
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