Answer: 
Step-by-step explanation:
x^2+y^2=r^2 --> subtract x^2 to other side
y^2=r^2-x^2 --> square root both sides
y=sqrt(r^2-x^2)
I found this online I hope it helps a little if not, then sorry.
Answer:
894.035793467 or roughly 894
Step-by-step explanation:
I square rooted it by using a calculator, and by working it out on paper.