Question 81537
Anytime you get an equation like {{{c^2=289}}}, in order to "undo" the "square" of the c, you will have to take the "square root" of both sides!  This means you must either 
     1.  recognize the answer (like for small numbers like {{{c^2=25}}}), etc. 
     2.  use a calculator
 or  3.  use a trial and error method like this.  If you know that 12^2=144 and 20^2 = 400, then c^2 = 289 must be somewhere between 12 and 20.  Then just use trial and error to see if you can find the number that works.  However, this is the hard way!!  The calculator works very well.


There is a fourth way that sometimes is helpful.  There are certain "special" triangles that come out even.  These are called "Pythagorean Triples".  The most famous four triangles are as follows:  
     1.  3,4, and 5
     2.  5, 12, and 13
     3.  8, 15, and 17
     4.  7, 24, and 25
OR- any multiple of these numbers, like 6, 8, 10 is a multiple of 3,4, 5.


Most special triangles that come out to be whole numbers on all three sides will be these numbers or multiples of these numbers.


R^2 at SCC