Using cosine theorem, let the coordinate of C be (0, y), C 2 = A 2+B 2-2 ABCOSC, and substitute the data: 10? =6? +y？ +4? +y？ Under the -2*√2/2* radical sign (6? +y？ ) * Under the root symbol (4? +y？ )。 . . . Just solve the equation.

Or tan 45 = 1 = tan (∠ BCO+∠ ACO). . . Alternative data is also acceptable. .