Question 620756
Hi, there--
.
We can solve this problem using the equation from the Pythagorean Theorem: {{{a^2+b^2=c^2}}}. First, we'll find the side length of the square. Then we'll find the area of the square using the side length.
.
Draw a picture of a square. 
.
Now draw in one of the diagonals from one corner to the opposite corner (for example, from the upper left corner to the lower right corner.)
.
Notice that you have two triangles inside the square. These are both right triangles because every corner of the square is a 90-degree angle.  Both triangles have the same shape, except that one is rotated upside down. The diagonal makes the hypotenuse of both triangles.
.
Let's have the variable s be the length of the sides of the square. 
.
Look at one of the right triangles. Notice that both legs have a length of s, and the hypotenuse has a length of 10.
.
Use the the Pythagorean Equation. Substitute s for a and b, and 10 for c.
.
{{{a^2+b^2=c^2}}}
{{{s^2+s^2=10^2}}}
.
Solve for s.
.
{{{2s^2=100}}}
{{{s^2=50}}}
{{{s=sqrt(50)}}}
.
Now we know that the side length is {{{sqrt(50)}}}. We can use the formula for the area of a square.
.
{{{A=s^2}}}
.
Substitute {{{sqrt(50)}}} for s in the formula.
.
{{{A=(sqrt(50))^2}}}
.
Taking the square root of a numer and squaring a number reciprocal operations--they undo each other (like adding and subtracting te same number.) This means that squaring the square root of 50 gives you 50.
.
The area of the square is 50 square centimeters.
.
Hope this helps, Feel free to email if you have questions about this.
.
Ms.Figgy
math.in.the.vortex@gmail.com