SOLUTION: ABCD is a parllelogram,AE perpendicular to DC and CF perpendicular to AD.If AB=16cm,AE=8cm and CF=10cm,find AD

 




Angle CDF = Angle ADE because they are opposite angles formed 
by two intersecting lines CE and AF

Angle CFD = Angle AED = 90° because AE perpendicular to 
DC and CF perpendicular to AD. 

Triangle CDF is similar to triangle ADE because they have
two angles with the same measure.  

 =  because of corresponding 
sides of similar triangles are proportional. 

CD = AB = 16cm because they are opposite sides of a parallelogram

Since CD = 16cm , CF = 10cm, AE = 8cm, the above proportion 
becomes:

 = 

Cross-multiplying,

 = 

 = 

 = 

 = 

Edwin