Let AB and CD be two trees such that AB=20 m, CD=28 m and BD=17 m
Draw BE⊥CD.
( 1 mark )
Then, ED=CD−AB=28−20=8 m.
In △BED, applying Pythagoras Theorem
BD2=BE2+DE2
( 0.5 marks )
⇒BE2=BD2−DE2
⇒BE2=172−82=289−64=225
⇒BE=√225=15 m
⇒AC=BE=15 m
( 0.5 marks )