In the 3B1B video live stream video "Trigonometry fundamentals | Ep. 2 Lockdown live math", Grant mentions, "I want a triangle where that adjacent is equal to 1" (58:11), in demonstrating the tangent segment on a given unit circle (from origin point O to point P). I'm confused why we need/want the adjacent to be equal to one, although I understand that the value in this case from point O to point P is 1, as he draws a unit circle.
From my understanding, the tangent is just the right angle segment from the point P intersecting to the x-axis. I want to understand his statement but I'm confused what else I don't understand about the tangent, what about $tan(\theta) = \frac{O}{A}$ necessitates the adjacent to be 1?
edit: Thank you @Joshua Wang! I was way overthinking things!