hyp = 5cm, adj = \(\frac{8cm}{2}\) 4cm, opp = xcm Pythagoras theorem: hyp\(^2\) = opp\(^2\) + adj\(^2\) 5\(^2\) = x\(^2\) + 4\(^2\) x\(^2\) = 25 - 16 x = \sqrt9 x = 3cm