Answer:
The formula to find the distance from point d to point a is:
 

Explanation:
We are given coordinate of the vertices of the parallelogram abcd as:
a(0,0) , b(a,0) , c(a,b) and d(0,b)
We know that the distance between the two points 
 is given by:
 is given by:

Hence,the formula that can be used to determine the distance from point d(0,b) to point a(0,0) is:
