Question 721187
Here is a step by step just for you! :)
Draw a triangle, then use Pythagorean Theorem. 
{{{a^2+b^2=c^2}}}
plug in the numbers for each
{{{(2b)^2+(b)^2=(60)^2}}}
solve.
{{{4b^2+b^2=3600}}}
add like terms.
{{{5b^2=3600}}}
divide by 5 on both sides
{{{(5b^2)/5=3600/5}}}
square root each side to get rid of b^2 to make it b.
{{{root(2,b^2)=root(2,720)}}}
Because 720 does not have a square root reduce the radical!
-one way of doing this is by "making a tree"
     720
     / \           
    12  60
   /\   /\         
  2  6 6 10
         /\
        2  5
With this "tree" you see all of the factors needed to make the radical {{{root(2,720)}}} 
With the numbers that are in a matching pair they can be taken out. Imagine the radical is a jail ceil and you need two people to get out will one of the pair of 6's would "help" the other get out. That way one of the 6's are out and the other.... he died and hero's death in the effort. So since there is a pair of 2's and 6's you take one 6 and one 2 outside of the radical and are multiplied together. Now with what is left they stay in the radical (not counting those who died saving there pair). So in this case the 5 is alone in the radical while 2 and 6 become 12 and party outside of the radical that 5 is in. Which looks like:
{{{12root(2,5)}}}
Now that we have simplified the radical we have what b would equal
{{{b=12root(2,5)}}} and {{{a=2*(12root(2,5))}}} which you then can multiple the 2 and 12 and get {{{a=24root(2,5)}}}.

Answers:
{{{b=12root(2,5)}}}
{{{a=24root(2,5)}}}