P²=✓q²-r² make r

Answer 1

r = ±√(q² - P²)

Answer 2

p²=√(q²-r²)
p^4 = q^2 - r^2
r^2 = q^2 - p^4
r = ±√(q^2 - p^4)

Answer 3

r = ±√(q² - p^4)