solve 2 / z ((0.16-0.135-z^2 (0.135-0.0411) / (567000000^2-z^2) ) tanh(z 0.000000389/2) + 567000000 z (0.135-0.0411) tanh(567000000 0.000000067/2)/(567000000^2-z^2)) -0.000000067 0.68 = 0 for z