Question

In $△ABC$, if $\angle B={90}^o$, $AC=5cm$, and $AB=3cm$ what is the length of $BC$?

Answer 1

In $△ABC,\angle ABC={90}^o$ ....... $\left(i\right)$ [Given]

$AC=5cm,AB=3cm$ ........ [Given]

From $\left(i\right)$

${AC}^2={AB}^2+{BC}^2$ ....... (By Pythagoras theorem)
$⟹{BC}^2={AC}^2-{AB}^2$
$⟹B{C}^2=5^2-3^2=25-9=16$
$\therefore BC=\sqrt{16}=4cm$