Per the title, what are some of the oldest books on analytic geometry out there with unsolved exercises? Maybe there are some hidden gems from before the 20th century out there.
As requested, here are some late 19th century and early 20th century textbooks on analytic geometry that contain unsolved exercises (an example page is shown for each entry). The list is not exhaustive, you can find more by querying Archive.org .)
An elementary treatise on solid geometry, by W. Steadman Aldis (1880)
Elements of analytic geometry, by Simon Newcomb (1884)
Elements of analytic geometry, George A. Wentworth (1886)
New Analytic Geometry, by Percey F. Smith (1912)
Analytic Geometry, by Maria M. Roberts and Julia T. Colpitts (1918)