I have a JPEG image with Exif data that I can use to get latitude, longitude, altitude. How can I determine whether a coordinate (latitude, longitude, altitude) is inside or outside the above image?
To get this information you also need the direction, North for instance. Then you get the angle of view and create infinite triangle. Then you can check if the coordinates are inside this triangle or not.
If you are searching for a formula to do this, it would be better to ask your question at math.stackexchange.com.
Also you should consider your understanding of "inside". If you have a hill, house, tree between camera and the coordinates, you will not see the point, but it will be within your angle of view (based on the photo).
The angle of view is a property of your lens. Moreover, based on your question at StackOverflow, you need the angle between the focal axis of a lens and the surface because you can't be sure your drone is perpendicular to the ground. In general your question has nothing to do with photography. It is mathematical.