For this you will be using the pythagorean theorem, aka [tex]leg^2+leg^2=hypotenuse^2[/tex] .
Firstly, plug in 4 and x into the leg variable and 10 into the hypotenuse variable: [tex]4^2+x^2=10^2[/tex] .
Next, solve the exponents, and you should get [tex]16+x^2=100[/tex]
Subtract 16 on each side to get [tex]x^2=84[/tex]
Then square root each side to get [tex]x= \sqrt{84}[/tex], which can be rewritten as [tex]2 \sqrt{21} [/tex] .
