9514 1404 393
Answer:
? = a
Explanation:
The triangle is marked as an isosceles right triangle with legs aligned to the x-and y-axes. The length of AB is the difference of x-coordinates, so is ...
a - 0 = a
The same length is the length of AC:
? - 0 = a
? = a
The coordinates are ...
A(0, 0)
B(a, 0)
C(0, a)
The correct value for ? is a.