Is "A Priori" Actually Possible?

            A priori knowledge sounds like an awesome idea conceptually; some things are out there that we just know. A triangle is a shape. A bachelor is a man. These kind of definitive concepts would be a great foundation for things, but is this all actually a priori knowledge? All of these that seem to be a priori, but they don’t seem to help with the furthering of knowledge. From what I know now, analytic a priori knowledge are just categorization. A triangle is a shape tells us nothing of a triangle; it just says what category of stuff a triangle is.

            But how a priori is that knowledge that we think is a priori? Before there were humans, were triangles shapes? Were there even triangles? Was the word “triangle” just a word that humans assigned to three sided figures? Was “bachelor” the word that we applied to single men?  Like I said earlier, a priori sounds like a great concept that would help greatly in philosophizing, but how true is it? I am very interested to see what Kant goes with a priori and synthetic judgments and how he shows they are possible.