Question 880922
Find the other leg using the Pythagorean theorem.
{{{L[1]^2+L[2]^2=H^2}}}
{{{L[1]^2+12^2=15^2}}}
{{{L[1]^2+144=225}}}
{{{L[1]^2=81}}}
{{{L[1]=9}}}
Then the area of a triangle is,
{{{A=(1/2)L[1]L[2]}}}
{{{A=(1/2)(9)(12)}}}
{{{A=54}}}{{{cm^2}}}