Question 546524
    the two perpendicular sides of a triangle are 4 and 8. what is the length of the third side
Since "two sides are perpendicular", it must be a "right triangle" -- you can now apply Pythagorean theorem:
Let x = third side
then
{{{4^2 + 8^2 = x^2}}}
{{{16 + 64 = x^2}}}
{{{80 = x^2}}}
{{{sqrt(80) = x}}}
{{{sqrt(2*2*2*2*5) = x}}}
{{{2*sqrt(2*2*5) = x}}}
{{{2*2*sqrt(5) = x}}}
{{{4*sqrt(5) = x}}} (exact answer)
OR
{{{8.944 = x}}} (approximate answer)