Question 347864
I think you mean right triangle.
Use the Pythagorean theorem where x is either a leg or the hypotenuse.
Leg:
{{{x^2+3^2=5^2 }}}
{{{x^2+9=25 }}}
{{{x^2=16 }}}
{{{x=4 }}}
.
.
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Hypotenuse:
{{{3^2+5^2=x^2 }}}
{{{9+25=x^2 }}}
{{{x^2=34 }}}
{{{ x=sqrt(34) }}}