Question 326629
I think you mean right triangle instead of hypotenuse triangle.
If it's a right triangle and you know one angle is 30, the other angle is 60. 
In terms of the hypotenuse, the two sides would be 
{{{A=H*cos(30)}}}
{{{B=H*sin(30)}}}
From your description, I'm not sure which one equals 10 (A or B).
We'll do it both ways.
{{{A=10}}}
{{{H*cos(30)=10}}}
{{{H*sqrt(3)/2=10}}}
{{{H=20/sqrt(3)}}}
{{{B=Hsin(30)}}}
{{{B=(20/sqrt(3))(1/2)=10/sqrt(3)}}}
{{{B=10sqrt(3)/3}}}
Not one of the choices, try the other.
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{{{B=10}}}
{{{Hsin(30)=10}}}
{{{H(1/2)=10}}}
{{{H=20}}}
{{{A=Hcos(30)}}}
{{{A=20*(sqrt(3)/2)}}}
{{{A=10sqrt(3)}}}
Looks like we have a winner since it's one of the choices.