How do I solve for this 1/√(5.22^2 +r^2)=1/1.33

1/√(5.22^2 +r^2)=1/1.33

then
√(5.22^2 +r^2) = 1.33
square both sides
27.2484 + r^2 = 1.7689
r^2 = -25.4795

r will be a complex number , r = ± √25.4795 i