Question 4353
Picture the right triangle formed by this 15 foot ladder against the wall.  The length of the ladder (15 feet) is the hypotenuse, and the legs of the triangle are the 10 feet distance from the bottom of the ladder to the wall, and also the height of the ladder, which is the unknown.


According to the Theorem of Pythagoras, 
{{{a^2 + b^2 = c^2}}}, where "c" is the hypotenuse, and the legs are "a" and "b".


{{{10^2 + x^2 = 15^2}}}

{{{100 + x^2 = 225}}}


Subtract 100 from each side:

{{{x^2 = 125}}}


Take the square root of each side:
{{{x = sqrt (125) or -sqrt(125)}}}


A side of a triangle cannot be negative, so the answer is 
{{{x = sqrt (125)}}} or simplify the radical
{{{x = sqrt (25) * sqrt (5)}}}

{{{x = 5 * sqrt (5)}}}


R^2 at SCC