Question: User: 28
90
90
90
456
456
456
456
u^2
1. The problem appears to involve angles and possibly a variable $u^2$.
2. Since the angles given are $90^\circ$ and $45^\circ$, these might relate to right triangles or angle sums.
3. Without additional context, let's consider the sum of angles or a relation involving $u^2$.
4. If the problem is to find $u^2$ given these angles, more information is needed.
5. Please provide more details or clarify the question for a precise solution.