f(ɑ, g(β)) = g(β)tan[SUP]-1[/SUP]((g(β)[SUP]ɑtan(g(β))[/SUP] - ɑsin[SUP]2[/SUP]sec[SUP]3[/SUP]([sup]ɑ[/sup]/[sub](g(β)[/sub]ɑ))) g(β) = 2β(1 - β[SUP]2[/SUP]tanβ) f '(5, g(g '(3)))/10. Not bad.