Excel Lambda function to find alpha value

GetAlpha.txt

/* 
A function to calculate alpha as given by Appendix G in SCI P398

INPUTS: m, m2 and e 
RETURNS: value of alpha

Example:
    =GetAlpha(40,45,35)
Returns:
    5.345
    
Note:
    The last optional parameter is used for recurrsion and should not be inputted by the user.
    The function does not check the validity of the input.
    The result is accurate to the nearest 0.005.
*/

GetAlpha = LAMBDA(m, m_2, e, [alpha_DONT_INPUT],
    LET(
        lambda_1, m / (m + e),
        lambda_2, m_2 / (m + e),
        alpha, IF(ISOMITTED(alpha_DONT_INPUT), 4.45, alpha_DONT_INPUT),
        lambda_1_temp, GetLambda1(alpha, lambda_2),
        IF(
            (lambda_1 / lambda_1_temp) < 1,
            GetAlpha(m, m_2, e, alpha + 0.005),
            MIN(alpha, 8.00)
        )
    )
);

GetLambda1 = LAMBDA(alpha, lambda_2,
    LET(
        lambda_1_lim, 1.25 / (alpha - 2.75),
        lambda_2_lim, alpha * lambda_1_lim / 2,
        IF(
            lambda_2 >= lambda_2_lim,
            lambda_1_lim,
            lambda_1_lim + (1 - lambda_1_lim) * ((lambda_2_lim - lambda_2) / lambda_2_lim) ^ (0.185 * alpha ^ 1.785)
        )
    )
);