Question 1023461
Sixty degrees where?  At the ground away from the wall?

L for length of the ladder;
{{{20/L=sin(60)}}}


{{{L/20=1/sin(60)}}}


{{{L=20/sin(60)}}}



{{{L=20(2/sqrt(3))}}}
{{{L=40/sqrt(3)}}}


Or if you prefer
{{{L=40*sqrt(3)/3}}}

{{{L=(40/3)sqrt(3)}}}