Answer:
x^2 + y^2 - 4y - 15 = 6
x^2 + y^2 - 4y = 21
x^2 + y^2 - 4y + 4 = 25
x^2 + (y - 2)^2 = 5^2
r = 5
AAS
A for <SUR and <TVR
A for <SRU and <TRV
S for SU and TV