How to solve nonlinear equations in LibreOffice Calc?

Question

I want to solve an equation that is an integration of Miner and Wöhler formulas:

\frac{n_1}{N_1} + \frac{n_2}{N_2} = 1

where:

• n1s are stored in column A (assume numbers in 10^6-10^8 range)
• n2s are stored in column B (assume numbers in 10^5-10^6 range)
• Nis including N1s and N2s are defined as:

log_{10} \left( N_i \right) = 7 \left( 1 - \frac{\sigma_{f_i} - \sigma_e}{\sigma_u - \sigma_e} \right)

• _u sigma_u is a global variable as instructed here. (assume 1300)
• and _fis
  • _f1s stored in column C (assume random numbers between 200-300 range)
  • _f2s stored in column D (assume random numbers between 200-300 range)

I tried looking into the "Solver for Nonlinear Programming" extension for Calc here, but I can't find proper documentation for that.

I can solve the nonlinear equation in Maxima/WxMaxima using the

find_root(n1 / N1 + n2 / N2 - 1, sigma_e, 200, 300);

function, but I don't know how to do it in LibreOffice Calc so I can map it to those columns.