Question 924424
Make two right triangles from the isosceles triangle by bisecting the vertex angle. The angle is then 40 degrees and the opposite side is 6 cm.
{{{sin(40)=OPP/HYP=6/HYP}}}
{{{HYP=6/sin(40)=9.33}}}
The perimeter is then,
{{{P=HYP+HYP+12}}}
{{{P=9.33(2)+12}}}
{{{P=18.66+12}}}
{{{P=30.66}}}{{{cm}}}