In a triangle ABC, perpendicular AD from A on BC meets at D. If BD=8 cm, DC=2 cm and AD=4 cm, then ___.
AC=2AB
In ΔADC,
AC2=AD2+DC2
⇒AC2=42+4=20
⇒AC=√20cm ... (i)
In △ADB,
AB2=42+82=80
⇒AB=√80=2√20 cm ... (ii)
From (i) and (ii,) we get AC=2AB