Use:
[tex]|AB|^2=|AC|^2+|BC|^2-2|AC||BC|\cos(m\angle ACB)[/tex]
We have:
[tex]|AC|=13;\ |BC|=29;\ m\angle ACB=41^o[/tex]
[tex]\cos41^o\approx0.7547[/tex]
substitute:
[tex]|AB|^2=13^2+29^6-2\cdot13\cdot29\cdot0.7547\\\\|AB|^2=440.9562\\\\|AB|\approx21[/tex]
