if b,h are given, and may simply be calculated. so i assume that are given, and you wish to find b and h.
from we get:
, which is a quadratic in h.
the discriminant is
however, aren't "independent" they both depend on the radius of the circle, r:
so , therefore: no real solutions for h.
however, in reviewing your original equations, it appears that your formula for either the area or the perimeter of the isoceles triangle is incorrect, if h is the height, then the perimeter length should be:
you might want to review that, and confirm (the calcuations get a lot messier if this is true).