Question

Pls answer this question I have maths examination tomorrow

Answer 1

In triangle ABC, since AB=AC,
Therefore angle ABD = angle ACD = angle ECF (angles opposite to equal sides are equal) (1)


Now in triangle ADB and triangle EFC,

Angle EFC = Angle ADB (90° each)

Angle ECF = Angle ABD (from (1))

Therefore triangle ADB is similar to triangle EFC by AA similarity Criterion.


Therefore,

AD/EF=AB/EC (similar triangles have corresponding sides proportional)

Or

AB×EF=AD×EC


Hence Proved.